fix dubious cache comparison check

in...

commit 083b7ca2
Date:   Tue Dec 26 15:58:21 2017 +0100

    Move PhysicalFontFace member of FontSelectPattern

this went from...

    if (
        (rA.mpFontData && rA.mpFontData->IsSymbolFont()) ||
        (rB.mpFontData && rB.mpFontData->IsSymbolFont())
       )

to ...

     if (rA.IsSymbolFont() && rB.IsSymbolFont())
     {

Change-Id: I1407573dfa73ac843b790ff3bc4ac0d5f66ab42c
Reviewed-on: https://gerrit.libreoffice.org/55183Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

vcl/source/font/fontcache.cxx

@@ -60,7 +60,7 @@ bool ImplFontCache::IFSD_Equal::operator()(const FontSelectPattern& rA, const Fo
 
     // Symbol fonts may recode from one type to another So they are only
     // safely equivalent for equal targets
-    if (rA.IsSymbolFont() && rB.IsSymbolFont())
+    if (rA.IsSymbolFont() || rB.IsSymbolFont())
     {
         if (rA.maTargetName != rB.maTargetName)
             return false;