[fix](Variant Type) Fixes the desc failure

[csun5285]

Proposed changes

Issue Number: close #xxx

fix the desc failure when there is no decomposition of columns in the variant column.

Further comments

If this is a relatively large or complex change, kick off the discussion at dev@doris.apache.org by explaining why you chose the solution you did and what alternatives you considered, etc...

[csun5285]

run buildall

[eldenmoon]

add case

[csun5285]

run buildall

[eldenmoon]

LGTM

[github-actions]

PR approved by at least one committer and no changes requested.

[github-actions]

PR approved by anyone and no changes requested.

[doris-robot]

(From new machine)TeamCity pipeline, clickbench performance test result:
the sum of best hot time: 44.64 seconds
stream load tsv: 593 seconds loaded 74807831229 Bytes, about 120 MB/s
stream load json: 19 seconds loaded 2358488459 Bytes, about 118 MB/s
stream load orc: 67 seconds loaded 1101869774 Bytes, about 15 MB/s
stream load parquet: 31 seconds loaded 861443392 Bytes, about 26 MB/s
insert into select: 28.8 seconds inserted 10000000 Rows, about 347K ops/s
storage size: 17219463537 Bytes

[doris-robot]

TPC-H test result on machine: 'aliyun_ecs.c7a.8xlarge_32C64G'

Tpch sf100 test result on commit cb63409f79de0c6946f182fcb1728835da269a23, data reload: false

run tpch-sf100 query with default conf and session variables
q1	48936	31814	31845	31814
q2	370	139	144	139
q3	1520	1226	1214	1214
q4	1117	921	898	898
q5	3222	3170	3183	3170
q6	270	148	137	137
q7	1004	498	479	479
q8	2143	2217	2184	2184
q9	6894	6885	6867	6867
q10	3265	3277	3289	3277
q11	341	207	197	197
q12	345	205	215	205
q13	4660	3837	3818	3818
q14	415	314	315	314
q15	787	1307	1332	1307
q16	443	385	376	376
q17	1030	589	547	547
q18	7859	7408	7064	7064
q19	1512	1358	1451	1358
q20	2144	368	303	303
q21	3097	2756	2767	2756
q22	364	278	278	278
Total cold run time: 91738 ms
Total hot run time: 68702 ms

run tpch-sf100 query with default conf and set session variable runtime_filter_mode=off
q1	30808	31849	31816	31816
q2	281	165	170	165
q3	3833	3596	3726	3596
q4	2409	2379	2361	2361
q5	5958	6033	5943	5943
q6	241	133	133	133
q7	3047	3397	3364	3364
q8	3554	3584	3576	3576
q9	10064	9198	9144	9144
q10	3965	4039	4060	4039
q11	801	917	1357	917
q12	759	600	597	597
q13	4283	3568	3541	3541
q14	483	424	435	424
q15	1161	1320	1333	1320
q16	507	456	469	456
q17	1895	1876	1844	1844
q18	8838	8316	8993	8316
q19	1732	1745	1750	1745
q20	3021	2580	2644	2580
q21	6544	6135	6150	6135
q22	493	412	418	412
Total cold run time: 94677 ms
Total hot run time: 92424 ms

[qidaye]

LGTM