Make sure strides have positive values before converting.

Patch by Peter Schlaile: peter schlaile de


git-svn-id: file:///var/local/repositories/mplayer/trunk/libswscale@25467 b3059339-0415-0410-9bf9-f77b7e298cf2

swscale.c

@@ -1681,7 +1681,7 @@ static int rgb2rgbWrapper(SwsContext *c, uint8_t* src[], int srcStride[], int sr
 
     if(conv)
     {
-        if (dstStride[0]*srcBpp == srcStride[0]*dstBpp)
+        if (dstStride[0]*srcBpp == srcStride[0]*dstBpp && srcStride[0] > 0)
             conv(src[0], dst[0] + dstStride[0]*srcSliceY, srcSliceH*srcStride[0]);
         else
         {