use already existing variable

Change-Id: I3f2781e2a041845e732046ea591a15c9bb21f1a5

vcl/source/fontsubset/sft.cxx

@@ -1096,7 +1096,7 @@ static sal_uInt32 getGlyph2(const sal_uInt8 *cmap, const sal_uInt32 nMaxCmapSize
             sal_uInt16* const pGlyph = (&(subHeader2s[0].idRangeOffset))
                      + (Int16FromMOTA(subHeader2s[0].idRangeOffset)/2)             /* + offset        */
                      + theLowByte                                                  /* + to_look       */
-                     - Int16FromMOTA(subHeader2s[0].firstCode)
+                     - firstCode
                      ;
             if (reinterpret_cast<sal_uInt8*>(pGlyph) - cmap < int(nMaxCmapSize) - 4)
                 return *pGlyph;