fix(pro:table): layout tool tree shouldn't show empty

[sallerli1]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines
• Tests for the changes have been added/updated or not needed
• Docs and demo have been added/updated or not needed

What is the current behavior?

布局工具中，当同时有固定列和普通列时，搜索内容为空会出现多个空状态

What is the new behavior?

不应当展示多个空状态，只展示一个空状态

Other information

[idux-bot]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.78%. Comparing base (96492f8) to head (9dabb05).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1891   +/-   ##
=======================================
  Coverage   90.78%   90.78%           
=======================================
  Files         359      359           
  Lines       35249    35250    +1     
  Branches     2807     2808    +1     
=======================================
+ Hits        32002    32003    +1     
  Misses       3247     3247           

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