[Bug] Can't add partitons to a table which has "colocate_with" property

[wyndia]

Describe the bug

Version: Apache Doris 0.12.0-rc03

To Reproduce

1. Create a table:

   CREATE TABLE `test` (
                          `date` date,
                          `userid` varchar(128)
   ) ENGINE=OLAP
   DUPLICATE KEY(`date`, `userid`)
   PARTITION BY RANGE(`date`)()
   DISTRIBUTED BY HASH(`userid`) BUCKETS 8
   PROPERTIES (
              "colocate_with" = "test"
          );

2. Try to add a partition:

   ALTER TABLE test add PARTITION p1 VALUES [("2020-10-15"), ("2020-10-16"));

3. See the error:

   ERROR 1064 (HY000): Unexpected exception: null

[EmmyMiao87]

The main reason for this is because your partition does not specify a range, so it is not a partitioned table

[HappenLee]

@wyndia Hi，I check this problem. because you create table with empty partition of date, this cause the colocatebalancer get null pointer.

it is easy to avoid this bug:

1. create table with unless one valid partition. do not empty partition and add partition later
2. use dynamic_partition.

[morningman]

@wyndia Hi，I check this problem. because you create table with empty partition of date, this cause the colocatebalancer get null pointer.

it is easy to avoid this bug:

1. create table with unless one valid partition. do not empty partition and add partition later
2. use dynamic_partition.

i think this is a bug, we should fix it