fdo#47689: Avoid crashing mdworker: Don't use uninitialized variable

It's the isCustom field that should be checked to see whether the
customAttribute field has been assigned or not.

Change-Id: I5d2af26b675ab0cbc0e1844eb98ebaf5145eb73d
Reviewed-on: https://gerrit.libreoffice.org/7417
Reviewed-by: Michael Stahl <mstahl@redhat.com>
Tested-by: Michael Stahl <mstahl@redhat.com>
diff --git a/extensions/source/macosx/spotlight/OOoMetaDataParser.m b/extensions/source/macosx/spotlight/OOoMetaDataParser.m
index a6ce40a..0f1bad9 100644
--- a/extensions/source/macosx/spotlight/OOoMetaDataParser.m
+++ b/extensions/source/macosx/spotlight/OOoMetaDataParser.m
@@ -172,7 +172,7 @@ static NSDictionary *metaXML2MDIKeys;
        }
        // cleanup part 1
        [textCurrentElement release];
        if (customAttribute != nil) {
        if (isCustom == YES) {
            [customAttribute release];
        }
    }