QIBusPlatformInputContext: Fix a crash in tst_qinputpanel::update.

Change-Id: If50c442958b6f25f17325f7792bb3f882e4b13e7
Reviewed-by: Pekka Vuorela <pekka.ta.vuorela@nokia.com>
Reviewed-by: Joona Petrell <joona.t.petrell@nokia.com>

src/plugins/platforminputcontexts/ibus/qibusplatforminputcontext.cpp

@@ -160,6 +160,8 @@ void QIBusPlatformInputContext::cursorRectChanged()
         return;
 
     QWindow *inputWindow = qApp->inputPanel()->inputWindow();
+    if (!inputWindow)
+        return;
     r.moveTopLeft(inputWindow->mapToGlobal(r.topLeft()));
     if (debug)
         qDebug() << "microFocus" << r;