Fix the issue when dealloc AnimatedImage's native View, the window does not exist and cause Crash

[dreampiggy]

[codecov]

Codecov Report

Merging #90 into master will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #90      +/-   ##
==========================================
+ Coverage   74.09%   74.12%   +0.03%     
==========================================
  Files           9        9              
  Lines         687      688       +1     
==========================================
+ Hits          509      510       +1     
  Misses        178      178              

Flag	Coverage Δ
#ios	74.12% <100.00%> (+0.03%)	⬆️

Impacted Files	Coverage Δ
SDWebImageSwiftUI/Classes/AnimatedImage.swift	72.59% <100.00%> (+0.07%)	⬆️

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