cppCheck bRet reassigned before used

Change-Id: Iaf27254896783deaeaee65bd51617d8e4e457873
Reviewed-on: https://gerrit.libreoffice.org/63244
Tested-by: Jenkins
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>

vcl/source/filter/graphicfilter2.cxx

@@ -450,7 +450,6 @@ bool GraphicDescriptor::ImpDetectPCX( SvStream& rStm )
     if ( cByte == 0x0a )
     {
         nFormat = GraphicFileFormat::PCX;
-        bRet = true;
 
         sal_uInt16  nTemp16;
         sal_uInt16  nXmin;