No divide by zero if all imageformat features are disabled

Change-Id: Ib3e8a4b62ae627bc3dc8541767dafff4e493d2f8
Reviewed-by: Tasuku Suzuki <tasuku.suzuki@qt.io>
Reviewed-by: Eirik Aavitsland <eirik.aavitsland@qt.io>

src/gui/image/qimagereader.cpp

@@ -471,7 +471,8 @@ static QImageIOHandler *createReadHandlerHelper(QIODevice *device,
 
             --numFormats;
             ++currentFormat;
-            currentFormat %= _qt_NumFormats;
+            if (currentFormat >= _qt_NumFormats)
+                currentFormat = 0;
         }
     }