Fixed insertion of the overlay_remove callback (SLAP_CONFIG_DELETE)

servers/slapd/backover.c

@@ -1214,8 +1214,12 @@ overlay_remove( BackendDB *be, slap_overinst *on, Operation *op )
 	rm_cb->sc_private = (void*) rm_ctx;
 
 	/* Append callback to the end of the list */
-	for ( cb = op->o_callback; cb->sc_next; cb = cb->sc_next );
-	cb->sc_next = rm_cb;
+	if ( !op->o_callback ) {
+		op->o_callback = rm_cb;
+	} else {
+		for ( cb = op->o_callback; cb->sc_next; cb = cb->sc_next );
+		cb->sc_next = rm_cb;
+	}
 }
 #endif /* SLAP_CONFIG_DELETE */