uitest: warn if the command is not executed

Change-Id: I53bfa5ef7594eeb7446cdb9e4ba211839e255197

vcl/source/uitest/uitest.cxx

@@ -18,10 +18,12 @@
 
 void UITest::executeCommand(const OUString& rCommand)
 {
-    comphelper::dispatchCommand(
+    bool bSuccess = comphelper::dispatchCommand(
         rCommand,
         {{"SynchronMode", -1, css::uno::Any(false),
           css::beans::PropertyState_DIRECT_VALUE}});
+
+    SAL_WARN_IF(!bSuccess, "uitest", "failed to execute command: " << rCommand);
 }
 
 std::unique_ptr<UIObject> UITest::getFocusTopWindow()