Fix UI for constraint deletion

[zhouzhuojie]

Description

Fix #290

Tested locally.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

[codecov-io]

Codecov Report

Merging #295 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master    #295   +/-   ##
======================================
  Coverage    81.8%   81.8%           
======================================
  Files          26      26           
  Lines        1533    1533           
======================================
  Hits         1254    1254           
  Misses        210     210           
  Partials       69      69

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