tdf#102382: nextEventMatchingMask should only be called from the Main Thread

So don't then unless we are on the main thread.

Change-Id: I6ba52ed7db5d73a4c1c6acf10bdf254a6f959da8

vcl/osx/salinst.cxx

@@ -736,6 +736,9 @@ bool AquaSalInstance::AnyInput( VclInputFlags nType )
         }
     }
 
+    if (![NSThread isMainThread])
+        return false;
+
     unsigned/*NSUInteger*/ nEventMask = 0;
     if( nType & VclInputFlags::MOUSE)
         nEventMask |=