Bug 1124535 - Check if we have a downscaler before using it in nsJPEGDecoder. r=tn

--HG--
extra : rebase_source : 8bcde149c51dc1ab731d7f331a80cf016983c79e

image/decoders/nsJPEGDecoder.cpp

@@ -537,7 +537,9 @@ nsJPEGDecoder::WriteInternal(const char* aBuffer, uint32_t aCount)
             break;
 
           mInfo.output_scanline = 0;
-          mDownscaler->ResetForNextProgressivePass();
+          if (mDownscaler) {
+            mDownscaler->ResetForNextProgressivePass();
+          }
         }
       }