title: Error MSB4018: The "ResolveSdks" monodevelop
body: <p>i had the following error in monodevelop:</p>
  
  <pre><code>C:\Program Files (x86)\MSBuild\Novell\Novell.MonoDroid.Common.targets(2,2): Error MSB4018: The "ResolveSdks" task failed unexpectedly.
  System.ArgumentNullException: Value cannot be null.
  Parameter name: path1
     at System.IO.Path.Combine(String path1, String path2, String path3)
     at Novell.MonoDroid.Build.Tasks.ResolveSdks.Execute()
     at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute()
     at Microsoft.Build.BackEnd.TaskBuilder.ExecuteInstantiatedTask(ITaskExecutionHost taskExecutionHost, TaskLoggingContext taskLoggingContext, TaskHost taskHost, ItemBucket bucket, TaskExecutionMode howToExecuteTask, Boolean&amp; taskResult) (MSB4018) (test)
  </code></pre>
  
  <p>how can i fix it?
  to change the version doesn't works</p>