Fix NRE when unexpected content is returned by the server

[pavel-mikula-sonarsource]

There's probably some issue in JSON parsing when server doesn't return expected content.

Better user-friendly message should be reported instead. Related to #1149

Steps to reproduce

Configure running website that does not have SQ on it:

sonarscanner.msbuild.exe /d:sonar.host.url="https://google.com" /k:"Something"

Error observed

NullReferenceException: Object reference not set to an instance of an object.

Preparing working directories...
17:00:00.001  Updating build integration targets...
17:00:00.115  Failed to request and parse 'https://google.com/api/server/version': Object reference not set to an instance of an object.

Unhandled Exception: System.NullReferenceException: Object reference not set to an instance of an object.
   at SonarScanner.MSBuild.PreProcessor.SonarWebService.<>c__DisplayClass18_0.<<DownloadServerVersion>b__0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at SonarScanner.MSBuild.PreProcessor.SonarWebService.<DoLogExceptions>d__17`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at SonarScanner.MSBuild.PreProcessor.SonarWebService.<DownloadServerVersion>d__18.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at SonarScanner.MSBuild.PreProcessor.SonarWebService.<GetServerVersion>d__13.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at SonarScanner.MSBuild.PreProcessor.SonarWebService.<WarnIfSonarQubeVersionIsDeprecated>d__9.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at SonarScanner.MSBuild.PreProcessor.TeamBuildPreProcessor.<DoExecute>d__12.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at SonarScanner.MSBuild.PreProcessor.TeamBuildPreProcessor.<Execute>d__11.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at SonarScanner.MSBuild.BootstrapperClass.<PreProcess>d__9.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at SonarScanner.MSBuild.BootstrapperClass.<Execute>d__8.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at SonarScanner.MSBuild.Program.<Execute>d__4.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at SonarScanner.MSBuild.Program.<Execute>d__3.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at SonarScanner.MSBuild.Program.<Main>d__2.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at SonarScanner.MSBuild.Program.<Main>(String[] args)

[sebastien-marichal]

This bug has been fixed in #1539 (as part of #1149).
I close this issue.