set number of read bytes correctly

It was wrong if we read less than was expected.

Thanks to Antti Levomäki and Christian Jalio from Forcepoint.

Change-Id: I070c1731d1aace4c101fa01efed0c28734c44899

writerperfect/source/common/WPXSvInputStream.cxx

@@ -877,7 +877,10 @@ const unsigned char *WPXSvInputStream::read(unsigned long numBytes, unsigned lon
     if (!mpImpl->mnReadBufferLength)
         return nullptr;
 
-    numBytesRead = numBytes;
+    if (numBytes <= mpImpl->mnReadBufferLength)
+        numBytesRead = numBytes;
+    else
+        numBytesRead = mpImpl->mnReadBufferLength;
 
     mpImpl->mnReadBufferPos += numBytesRead;
     return mpImpl->mpReadBuffer;