Bug fix of type check in ListEdit

[hanjinliu]

This PR fixes a bug in ListEdit.
I found ListEdit could not deal with type annotation of list[...] with an empty list as the default value.

@magicgui
def f(x: list[int]): ...  # OK

@magicgui
def f(x: list[int] = []): ...  # Error!

[codecov]

Codecov Report

Merging #404 (a4f755b) into main (876190a) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #404   +/-   ##
=======================================
  Coverage   88.64%   88.64%           
=======================================
  Files          30       30           
  Lines        3804     3804           
=======================================
  Hits         3372     3372           
  Misses        432      432           

Impacted Files	Coverage Δ
magicgui/widgets/_concrete.py	85.42% <100.00%> (ø)

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[tlambert03]

thanks!