MDEV-7538: Wrong constraint (TINYINT or MEDIUMINT and INT)

causes server crash

Analysis: If wrong data types used on foreign constraint there
was possibility that foreign->id is NULL when incorrect
foreign constraint was removed from the dictionary cache.

Fix: Add guard foreign->id != NULL before trying to lookup
or remove the foreign constraint from dictionary cache.

Tested using user database where problem was repeatable.

storage/innobase/dict/dict0dict.c

@@ -2530,7 +2530,7 @@ dict_foreign_remove_from_cache(
 
 		rbt = foreign->referenced_table->referenced_rbt;
 
-		if (rbt != NULL) {
+		if (rbt != NULL && foreign->id != NULL) {
 			const ib_rbt_node_t*	node
 				= rbt_lookup(rbt, foreign->id);
 			dict_foreign_t*	val = *(dict_foreign_t**) node->value;
@@ -2549,7 +2549,7 @@ dict_foreign_remove_from_cache(
 			       foreign);
 		rbt = foreign->foreign_table->foreign_rbt;
 
-		if (rbt != NULL) {
+		if (rbt != NULL && foreign->id != NULL) {
 			const ib_rbt_node_t*	node
 				= rbt_lookup(rbt, foreign->id);
 			dict_foreign_t*	val = *(dict_foreign_t**) node->value;

storage/xtradb/dict/dict0dict.c

@@ -2650,10 +2650,16 @@ dict_foreign_remove_from_cache(
 			       foreign);
 
 		rbt = foreign->referenced_table->referenced_rbt;
-		if (rbt != NULL) {
+		if (rbt != NULL && foreign->id != NULL) {
+			const ib_rbt_node_t*	node
+				= rbt_lookup(rbt, foreign->id);
+			dict_foreign_t*	val = *(dict_foreign_t**) node->value;
+
+			if (val == foreign) {
 				rbt_delete(rbt, foreign->id);
 			}
 		}
+	}
 
 	if (foreign->foreign_table) {
 		ib_rbt_t*	rbt;
@@ -2663,10 +2669,16 @@ dict_foreign_remove_from_cache(
 			       foreign);
 		rbt = foreign->foreign_table->foreign_rbt;
 
-		if (rbt != NULL) {
+		if (rbt != NULL && foreign->id != NULL) {
+			const ib_rbt_node_t*	node
+				= rbt_lookup(rbt, foreign->id);
+			dict_foreign_t*	val = *(dict_foreign_t**) node->value;
+
+			if (val == foreign) {
 				rbt_delete(rbt, foreign->id);
 			}
 		}
+	}
 
 	dict_foreign_free(foreign);