Bug#48276: can't add column if subpartition exists

Bug when setting up default partitioning,
used an uninitialized variabe.

mysql-test/r/partition.result:
  Bug#48276: can't add column if subpartition exists
  
  Added result
mysql-test/t/partition.test:
  Bug#48276: can't add column if subpartition exists
  
  Added test
sql/sql_partition.cc:
  Bug#48276: can't add column if subpartition exists
  
  even if is_create_table_ind was set, one tried to set no_subparts
  with the unitialized no_parts local variable.
  
  Fixed by rearrange the code to be to only execute
  the statements when is_create_table_ind was not set.

mysql-test/r/partition.result

 drop table if exists t1, t2;
+CREATE TABLE t1 (a INT, b INT)
+PARTITION BY LIST (a)
+SUBPARTITION BY HASH (b)
+(PARTITION p1 VALUES IN (1));
+ALTER TABLE t1 ADD COLUMN c INT;
+DROP TABLE t1;
 CREATE TABLE t1 (
 a int NOT NULL,
 b int NOT NULL);

mysql-test/t/partition.test

@@ -14,6 +14,15 @@
 drop table if exists t1, t2;
 --enable_warnings
 
+#
+# Bug#48276: can't add column if subpartition exists
+CREATE TABLE t1 (a INT, b INT)
+PARTITION BY LIST (a)
+SUBPARTITION BY HASH (b)
+(PARTITION p1 VALUES IN (1));
+ALTER TABLE t1 ADD COLUMN c INT;
+DROP TABLE t1;
+
 #
 # Bug#46639: 1030 (HY000): Got error 124 from storage engine on
 # INSERT ... SELECT ...

sql/sql_partition.cc

@@ -196,10 +196,11 @@ bool partition_default_handling(TABLE *table, partition_info *part_info,
 {
   DBUG_ENTER("partition_default_handling");
 
+  if (!is_create_table_ind)
+  {
     if (part_info->use_default_no_partitions)
     {
-    if (!is_create_table_ind &&
-        table->file->get_no_parts(normalized_path, &part_info->no_parts))
+      if (table->file->get_no_parts(normalized_path, &part_info->no_parts))
       {
         DBUG_RETURN(TRUE);
       }
@@ -208,14 +209,14 @@ bool partition_default_handling(TABLE *table, partition_info *part_info,
              part_info->use_default_no_subpartitions)
     {
       uint no_parts;
-    if (!is_create_table_ind &&
-        (table->file->get_no_parts(normalized_path, &no_parts)))
+      if (table->file->get_no_parts(normalized_path, &no_parts))
       {
         DBUG_RETURN(TRUE);
       }
       DBUG_ASSERT(part_info->no_parts > 0);
-    part_info->no_subparts= no_parts / part_info->no_parts;
       DBUG_ASSERT((no_parts % part_info->no_parts) == 0);
+      part_info->no_subparts= no_parts / part_info->no_parts;
+    }
   }
   part_info->set_up_defaults_for_partitioning(table->file,
                                               (ulonglong)0, (uint)0);