[QFontDatabase] Don't look for best foundry twice

In case the foundry name was empty and foundry lookup has failed, don't
look for *any* foundry since it does exactly the same as previous call.

Change-Id: I2a81949df06c31e1ae6999a6bbbe973408d4b814
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@theqtcompany.com>
Reviewed-by: Pierre Rossi <pierre.rossi@theqtcompany.com>

src/gui/text/qfontdatabase.cpp

@@ -1166,7 +1166,7 @@ static int match(int script, const QFontDef &request,
             bestFoundry(script, score, request.styleStrategy,
                         test.family, foundry_name, styleKey, request.pixelSize, pitch,
                         &test, force_encoding_id, request.styleName);
-        if (test.foundry == 0) {
+        if (test.foundry == 0 && !foundry_name.isEmpty()) {
             // the specific foundry was not found, so look for
             // any foundry matching our requirements
             newscore = bestFoundry(script, score, request.styleStrategy, test.family,