Prevent StackOverflow in ParseTrailer and fix #1122

[BobLd]

No description provided.

[BobLd]

System.IO.FileNotFoundException: Could not find 'mono' host. Make sure that 'mono' is installed on the machine and is available in PATH environment variable.
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Helpers.DotnetHostHelper.GetMonoPath() in /_/src/Microsoft.TestPlatform.CoreUtilities/Helpers/DotnetHostHelper.cs:line 93
   at Microsoft.VisualStudio.TestPlatform.CrossPlatEngine.Hosting.DefaultTestHostManager.GetTestHostProcessStartInfo(IEnumerable`1 sources, IDictionary`2 environmentVariables, TestRunnerConnectionInfo connectionInfo) in /_/src/Microsoft.TestPlatform.TestHostProvider/Hosting/DefaultTestHostManager.cs:line 219

Unclear what is the issue with the MacOS tests - will have a look