Merge pull request #70 from vinnyrom/vinnyrom

Fix null dereference of 'progress' when updating an archive.

CPP/7zip/Compress/ZstdDecoder.cpp

@@ -127,8 +127,11 @@ HRESULT CDecoder::CodeSpec(ISequentialInStream * inStream,
       if (zOut.pos) {
         RINOK(WriteStream(outStream, _dstBuf, zOut.pos));
         _processedOut += zOut.pos;
+        if (progress)
+        {
           RINOK(progress->SetRatioInfo(&_processedIn, &_processedOut));
         }
+      }
 
       /* finished with buffer */
       if (zIn.pos == zIn.size)