pAvailGrammarSvcs can be reset to 0 on error

e.g. java grammar checker installed and java
disabled at runtime

Change-Id: I84b0e5eeb3ef9c30e153cb5fb65e35270023cd34

linguistic/source/lngsvcmgr.cxx

@@ -1152,7 +1152,7 @@ void LngSvcMgr::GetAvailableGrammarSvcs_Impl()
                     }
                 }
 
-                if (xSvc.is())
+                if (xSvc.is() && pAvailGrammarSvcs)
                 {
                     OUString            aImplName;
                     uno::Sequence< sal_Int16 >   aLanguages;