Fix security issue CVE-2015-1860

[taken from RedHat Qt3 patches]
(cherry picked from commit 094708c0e7)

src/kernel/qasyncimageio.cpp

@@ -1226,6 +1226,8 @@ void TQGIFFormat::fillRect(TQImage& img, int col, int row, int w, int h, TQRgb c
 
 void TQGIFFormat::nextY(TQImage& img, TQImageConsumer* consumer)
 {
+    if (out_of_bounds)
+        return;
     int my;
     switch (interlace) {
       case 0: