Getting error: actool exited with code 255

I am getting the following exception when trying to build my Xamarin.Forms iOS project...
Target _CoreCompileImageAssets: Tool /Applications/Xcode.app/Contents/Developer/usr/bin/actool execution started with arguments: --errors --warnings --notices --output-format xml1 --output-partial-info-plist "/Volumes/MacBook Pro Backup/Xamarin/NSE/iOS/obj/iPhoneSimulator/Debug/device-builds/iphone7.1-11.3/actool/partial-info.plist" --app-icon AppIcons --launch-image LaunchImage --compress-pngs --filter-for-device-model iPhone7,1 --target-device iphone --minimum-deployment-target 7.1 --platform iphonesimulator --compile "/Volumes/MacBook Pro Backup/Xamarin/NSE/iOS/obj/iPhoneSimulator/Debug/device-builds/iphone7.1-11.3/actool/bundle" "/Volumes/MacBook Pro Backup/Xamarin/NSE/iOS/obj/iPhoneSimulator/Debug/device-builds/iphone7.1-11.3/actool/cloned-assets/Resources/Images.xcassets" /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error : actool exited with code 255 /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: The "ACTool" task failed unexpectedly. /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: System.ArgumentException: Failed to parse PList data type: ---> System.ArgumentException: Must specify valid information for parsing in the string. /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: at System.Enum+EnumResult.SetFailure (System.Enum+ParseFailureKind failure, System.String failureMessageID, System.Object failureMessageFormatArgument) [0x00024] in /Users/builder/jenkins/workspace/build-package-osx-mono/2017-12/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/enum.cs:318 /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: at System.Enum.TryParseEnum (System.Type enumType, System.String value, System.Boolean ignoreCase, System.Enum+EnumResult& parseResult) [0x00077] in /Users/builder/jenkins/workspace/build-package-osx-mono/2017-12/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/enum.cs:396 /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: at System.Enum.Parse (System.Type enumType, System.String value, System.Boolean ignoreCase) [0x00010] in /Users/builder/jenkins/workspace/build-package-osx-mono/2017-12/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/enum.cs:370 /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: at System.Enum.Parse (System.Type enumType, System.String value) [0x00000] in /Users/builder/jenkins/workspace/build-package-osx-mono/2017-12/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/enum.cs:362 /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: at Xamarin.MacDev.PropertyListFormat+XmlFormat+Context.ReadObjectHead () [0x00018] in <35965be2bb8347aa861de1a3bb9a5f2b>:0 /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: --- End of inner exception stack trace --- /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: at Xamarin.MacDev.PropertyListFormat+XmlFormat+Context.ReadObjectHead () [0x00048] in <35965be2bb8347aa861de1a3bb9a5f2b>:0 /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: at Xamarin.MacDev.PropertyListFormat+XmlFormat+Context..ctor (System.Xml.XmlReader reader) [0x0000f] in <35965be2bb8347aa861de1a3bb9a5f2b>:0 /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: at Xamarin.MacDev.PropertyListFormat+XmlFormat.StartReading (System.IO.Stream input) [0x0008a] in <35965be2bb8347aa861de1a3bb9a5f2b>:0 /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: at Xamarin.MacDev.PropertyListFormat.CreateReadContext (System.IO.Stream input) [0x00010] in <35965be2bb8347aa861de1a3bb9a5f2b>:0 /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: at Xamarin.MacDev.PObject.FromFile (System.String fileName, System.Boolean& isBinary) [0x00024] in <35965be2bb8347aa861de1a3bb9a5f2b>:0 /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: at Xamarin.MacDev.PDictionary.FromFile (System.String fileName, System.Boolean& isBinary) [0x00001] in <35965be2bb8347aa861de1a3bb9a5f2b>:0 /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: at Xamarin.MacDev.PDictionary.FromFile (System.String fileName) [0x00001] in <35965be2bb8347aa861de1a3bb9a5f2b>:0 /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: at Xamarin.MacDev.Tasks.XcodeCompilerToolTask.Compile (Microsoft.Build.Framework.ITaskItem[] items, System.String output, Microsoft.Build.Framework.ITaskItem manifest) [0x002d0] in <35965be2bb8347aa861de1a3bb9a5f2b>:0 /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: at Xamarin.MacDev.Tasks.ACToolTaskBase.Execute () [0x009ba] in <35965be2bb8347aa861de1a3bb9a5f2b>:0 /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute () [0x00023] in /Users/builder/jenkins/workspace/build-package-osx-mono/2017-12/external/bockbuild/builds/msbuild-15/src/Build/BackEnd/TaskExecutionHost/TaskExecutionHost.cs:631 /Library/Frameworks/Mono.framework/External/xbuild/Xamarin/iOS/Xamarin.iOS.Common.targets(1211,3): error MSB4018: at Microsoft.Build.BackEnd.TaskBuilder+<ExecuteInstantiatedTask>d__26.MoveNext () [0x00212] in /Users/builder/jenkins/workspace/build-package-osx-mono/2017-12/external/bockbuild/builds/msbuild-15/src/Build/BackEnd/Components/RequestBuilder/TaskBuilder.cs:787 Done building target "_CoreCompileImageAssets" in project "NSE.iOS.csproj" -- FAILED.