Qt Ui Code Model: Don't try to run a empty string if no qtversion is set

Change-Id: I04eedaad849ad744a98f2ca8dc7883d0b3bafd9b
Reviewed-by: Daniel Teske <daniel.teske@nokia.com>

src/plugins/cpptools/uicodecompletionsupport.cpp

@@ -138,6 +138,8 @@ bool UiCodeModelSupport::runUic(const QString &ui) const
 {
     QProcess process;
     const QString uic = uicCommand();
+    if (uic.isEmpty())
+        return false;
     process.setEnvironment(environment());
 
     if (debug)