refactor(web): handle cesium private property of shadow map

[airslice]

Overview

• Handle private property of cesium shadowMap as optional property.
• Throw an error if these private property is undefined.

What I've done

What I haven't done

How I tested

Which point I want you to review particularly

Memo

[netlify]

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Name	Link
🔨 Latest commit	5a41279
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[codecov]

Codecov Report

Merging #531 (5a41279) into main (de536e8) will increase coverage by 0.01%.
The diff coverage is 0.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #531      +/-   ##
==========================================
+ Coverage   26.65%   26.67%   +0.01%     
==========================================
  Files        1342     1342              
  Lines      144699   144512     -187     
  Branches     3485     3485              
==========================================
- Hits        38571    38545      -26     
+ Misses     105005   104845     -160     
+ Partials     1123     1122       -1     

Flag	Coverage Δ
web	23.98% <0.00%> (-0.01%)	⬇️
web-beta	23.98% <0.00%> (-0.01%)	⬇️
web-classic	23.98% <0.00%> (-0.01%)	⬇️
web-utils	23.98% <0.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
web/src/beta/lib/core/engines/Cesium/hooks.ts	0.00% <0.00%> (ø)

... and 50 files with indirect coverage changes

[pyshx]

LGTM!