MTOUCH : error MT4116: Could not register the assembly '<redacted>': System.NullReferenceException: Object reference not set to an instance of an object

[kdubau]

Description

Recent regression (in last ~1 day) on master causing a build failure.

2018-02-15T22:17:54.7097910Z MTOUCH : error MT4116: Could not register the assembly '<redacted>': System.NullReferenceException: Object reference not set to an instance of an object [/Users/vsts/agent/2.129.0/work/1/s/src/<redacted>.csproj]
2018-02-15T22:17:54.7167870Z     at Registrar.StaticRegistrar.GetProtocolAttribute (Mono.Cecil.TypeReference type) [0x00001] in /Users/builder/data/lanes/1381/3f14eeea/source/xamarin-macios/tools/common/StaticRegistrar.cs:1311 
2018-02-15T22:17:54.7251510Z     at Registrar.Registrar.GetProtocols (Registrar.Registrar+ObjCType type, System.Collections.Generic.List`1[System.Exception]& exceptions) [0x00165] in /Users/builder/data/lanes/1381/3f14eeea/source/xamarin-macios/src/ObjCRuntime/Registrar.cs:1674 
2018-02-15T22:17:54.7311110Z     at Registrar.Registrar.RegisterTypeUnsafe (Mono.Cecil.TypeReference type, System.Collections.Generic.List`1[System.Exception]& exceptions) [0x001ee] in /Users/builder/data/lanes/1381/3f14eeea/source/xamarin-macios/src/ObjCRuntime/Registrar.cs:1901 
2018-02-15T22:17:54.7378360Z     at Registrar.Registrar.RegisterAssembly (Mono.Cecil.AssemblyDefinition assembly) [0x0009a] in /Users/builder/data/lanes/1381/3f14eeea/source/xamarin-macios/src/ObjCRuntime/Registrar.cs:2376 

Environment

Failed build http://build.devdiv.io/1390450

• xamarin.ios-11.9.0.215
• MonoFramework-MDK-5.10.0.107

Regression status

Last successful build http://build.devdiv.io/1385799

• xamarin.ios-11.9.0.170
• MonoFramework-MDK-5.10.0.107

Build Logs

Available in the CI build links, the failed job can be rebuilt with /v:diag if needed.