sax: there is no OUStringBuffer(char) ctor

Change-Id: I1811dead8f104a445bfee9282a60ecedeca872ed

sax/source/fastparser/fastparser.cxx

@@ -546,7 +546,7 @@ OUString lclGetErrorMessage( xmlParserCtxtPtr ctxt, const OUString& sSystemId, s
         pMessage = error->message;
     else
         pMessage = "unknown error";
-    OUStringBuffer aBuffer( '[' );
+    OUStringBuffer aBuffer( "[" );
     aBuffer.append( sSystemId );
     aBuffer.append( " line " );
     aBuffer.append( nLine );