fix(datastore): fix NPE when list diff without sparse element type inited

[jialeicui]

Description

Modules

• [ ] UI
• [x] Controller
• [ ] Agent
• [ ] Client
• [ ] Python-SDK
• [ ] Others

Checklist

• [ ] run code format and lint check
• [x] add unit test
• [ ] add necessary doc

[codecov[bot]]

Codecov Report

Merging #2974 (8dc9bc3) into main (e942bd1) will decrease coverage by 8.93%. The diff coverage is 90.90%.

@@             Coverage Diff              @@
##               main    #2974      +/-   ##
============================================
- Coverage     82.98%   74.05%   -8.93%     
- Complexity     3100     3106       +6     
============================================
  Files           558      432     -126     
  Lines         30308    15091   -15217     
  Branches       1816     1759      -57     
============================================
- Hits          25151    11176   -13975     
+ Misses         4354     3114    -1240     
+ Partials        803      801       -2     

Flag	Coverage Δ
console	?
controller	74.05% <90.90%> (+0.03%)	:arrow_up:
standalone	?
unittests	?

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...ava/ai/starwhale/mlops/datastore/ColumnSchema.java	76.62% <90.90%> (+1.92%)	:arrow_up:

... and 129 files with indirect coverage changes