potential deref of empty xStateSet

Change-Id: I83d876b0d966b18cdf85249b7e856e4e4f4dec27
Reviewed-on: https://gerrit.libreoffice.org/43488Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

svx/source/accessibility/AccessibleShape.cxx

@@ -460,7 +460,7 @@ uno::Reference<XAccessibleStateSet> SAL_CALL
             xStateSet.set( new ::utl::AccessibleStateSetHelper (*pStateSet));
         }
     }
-    if (!bDisposed && mpParent && mpParent->IsDocumentSelAll())
+    if (!bDisposed && xStateSet.is() && mpParent && mpParent->IsDocumentSelAll())
     {
         ::utl::AccessibleStateSetHelper* pStateSet =
             static_cast< ::utl::AccessibleStateSetHelper*>(xStateSet.get());