fixes a memory leak that appeared in tdf#93392 valgrind trace

Change-Id: Ifd4c6594d50ff63235e75049bc7ab8bc79606fc8
Reviewed-on: https://gerrit.libreoffice.org/17880Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

vcl/generic/glyphs/glyphcache.cxx

@@ -60,6 +60,8 @@ void GlyphCache::InvalidateAllGlyphs()
     for( FontList::iterator it = maFontList.begin(), end = maFontList.end(); it != end; ++it )
     {
         ServerFont* pServerFont = it->second;
+        // free all pServerFont related data
+        pServerFont->GarbageCollect( mnLruIndex+0x10000000 );
         mrPeer.RemovingFont(*pServerFont);
         delete pServerFont;
     }