starmath: SvStream::ReadBytes() returns std::size_t, not sal_uLong

Change-Id: I734e653343dcc563f1eb2312e5136fa5efe0f5fa
Reviewed-on: https://gerrit.libreoffice.org/38701Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Takeshi Abe <tabe@fixedpoint.jp>

starmath/source/smdetect.cxx

@@ -96,7 +96,7 @@ OUString SAL_CALL SmFilterDetect::detect( Sequence< PropertyValue >& lDescriptor
         aBuffer[nBufferSize] = 0;
         pInStrm->Seek( STREAM_SEEK_TO_BEGIN );
         pInStrm->StartReadingUnicodeText( RTL_TEXTENCODING_DONTKNOW ); // avoid BOM marker
-        sal_uLong nBytesRead = pInStrm->ReadBytes( aBuffer, nBufferSize );
+        auto nBytesRead = pInStrm->ReadBytes( aBuffer, nBufferSize );
         if (nBytesRead >= 6)
         {
             bool bIsMathType = false;