int_aggregate's int_enum() doesn't work correctly with arrays that

aren't 1-D, so give an error message instead of failing.  Per report
from Ron Mayer.

contrib/intagg/int_aggregate.c

@@ -242,6 +242,9 @@ int_enum(PG_FUNCTION_ARGS)
 			pc->p = p;
 			pc->flags = 0;
 		}
+		/* Now that we have a detoasted array, verify dimensions */
+		if (pc->p->a.ndim != 1)
+			elog(ERROR, "int_enum only accepts 1-D arrays");
 		pc->num = 0;
 		fcinfo->context = (Node *) pc;
 		MemoryContextSwitchTo(oldcontext);