Don't crash if focus issues arise.

The test has some strict focus requirements, but if they are not met
then the test should FAIL with a bit of explanation instead of crash.

Change-Id: I796e8a8092833f3413b3dc98a22466575dfe241d
Reviewed-by: Yann Bodson <yann.bodson@nokia.com>

tests/auto/qtquick2/qquicktextinput/tst_qquicktextinput.cpp

@@ -1527,6 +1527,7 @@ void tst_qquicktextinput::positionAt()
     textinputObject->setCursorPosition(0);
 
     {   QInputMethodEvent inputEvent(preeditText, QList<QInputMethodEvent::Attribute>());
+        QVERIFY(qGuiApp->focusObject());
         QGuiApplication::sendEvent(qGuiApp->focusObject(), &inputEvent); }
 
     // Check all points within the preedit text return the same position.
@@ -1539,6 +1540,7 @@ void tst_qquicktextinput::positionAt()
     QCOMPARE(textinputObject->positionToRectangle(1).x(), x1);
 
     {   QInputMethodEvent inputEvent;
+        QVERIFY(qGuiApp->focusObject());
         QGuiApplication::sendEvent(qGuiApp->focusObject(), &inputEvent); }
 
     // With wrapping.