MDEV-11572 JSON_DEPTH returns wrong results.

        JSON depth calculation fixed.

mysql-test/r/func_json.result

@@ -405,6 +405,9 @@ json_depth('[[], {}]')
 select json_depth('[[[1,2,3],"s"], {}, []]');
 json_depth('[[[1,2,3],"s"], {}, []]')
 4
+select json_depth('[10, {"a": 20}]');
+json_depth('[10, {"a": 20}]')
+3
 select json_length('');
 json_length('')
 NULL

mysql-test/t/func_json.test

@@ -163,6 +163,7 @@ select cast(NULL AS JSON);
 select json_depth(cast(NULL as JSON));
 select json_depth('[[], {}]');
 select json_depth('[[[1,2,3],"s"], {}, []]');
+select json_depth('[10, {"a": 20}]');
 
 select json_length('');
 select json_length('{}');

sql/item_jsonfunc.cc

@@ -1624,6 +1624,7 @@ longlong Item_func_json_depth::val_int()
     switch (je.state)
     {
     case JST_VALUE:
+    case JST_KEY:
       if (inc_depth)
       {
         c_depth++;