fix: table header broken when scroll do not have the data(#594)

[geekrainy]

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After:

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[geekrainy]

@zombieJ

[codecov]

Codecov Report

Merging #595 (8a6a278) into master (d5c3bae) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 8a6a278 differs from pull request most recent head a851a30. Consider uploading reports for the commit a851a30 to get more accurate results

@@           Coverage Diff           @@
##           master     #595   +/-   ##
=======================================
  Coverage   99.75%   99.75%           
=======================================
  Files          26       26           
  Lines         811      812    +1     
  Branches      237      238    +1     
=======================================
+ Hits          809      810    +1     
  Misses          2        2           

Impacted Files	Coverage Δ
src/Header/FixedHeader.tsx	100.00% <100.00%> (ø)
src/Table.tsx	100.00% <100.00%> (ø)

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[xrkffgg]

空数据的时候 头部不能变？

[geekrainy]

@xrkffgg 对，如果列很多，空数据头部会被挤成很窄的情况，和有数据的状态下表现不一致。

[xrkffgg]

+ rc-table@7.13.3