Fix bug #13424 locking view with query cache enabled crashes server

For LOCK view is opened but not prepared thus leaving 'table' field set to
NULL. invalidate_locked_for_write() wasn't checking that and call to 
invalidate_table(NULL) crashes server.

To invalidate_locked_for_write() added check that ensures that table is
completely opened.


sql/sql_cache.cc:
  Fix bug #13424 locking view with query cache enabled crashes server
  Added check that table is completely opened.
mysql-test/t/view_query_cache.test:
  Test case for bug#13424 locking view with query cache enabled crashes server
mysql-test/r/view_query_cache.result:
  Test case for bug#13424 locking view with query cache enabled crashes server

mysql-test/r/view_query_cache.result

@@ -123,4 +123,13 @@ select * from v3;
 a	b
 drop view v3;
 drop table t1, t2;
+create table t1(f1 int);
+insert into t1 values(1),(2),(3);
+create view v1 as select * from t1;
+set query_cache_wlock_invalidate=1;
+lock tables v1 read /*!32311 local */;
+unlock tables;
+set query_cache_wlock_invalidate=default;
+drop view v1;
+drop table t1;
 set GLOBAL query_cache_size=default;

mysql-test/t/view_query_cache.test

@@ -84,4 +84,16 @@ select * from v3;
 drop view v3;
 drop table t1, t2;
 
+#
+# Bug #13424 locking view with query cache enabled crashes server
+#
+create table t1(f1 int);
+insert into t1 values(1),(2),(3);
+create view v1 as select * from t1;
+set query_cache_wlock_invalidate=1;
+lock tables v1 read /*!32311 local */;
+unlock tables;
+set query_cache_wlock_invalidate=default;
+drop view v1;
+drop table t1;
 set GLOBAL query_cache_size=default;

sql/sql_cache.cc

@@ -1295,7 +1295,8 @@ void Query_cache::invalidate_locked_for_write(TABLE_LIST *tables_used)
       DUMP(this);
       for (; tables_used; tables_used= tables_used->next_local)
       {
-	if (tables_used->lock_type & (TL_WRITE_LOW_PRIORITY | TL_WRITE))
+        if (tables_used->lock_type & (TL_WRITE_LOW_PRIORITY | TL_WRITE) &&
+            tables_used->table)
 	  invalidate_table(tables_used->table);
       }
     }