Fix background abnormal when there are multiple scenes

[cptbtptpbcptdtptp]

No description provided.

[codecov]

Codecov Report

Patch coverage: 76.92% and project coverage change: -0.05% ⚠️

Comparison is base (8c4cffc) 65.08% compared to head (e5b333a) 65.03%.

❗ Current head e5b333a differs from pull request most recent head 5603b0d. Consider uploading reports for the commit 5603b0d to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1773      +/-   ##
==========================================
- Coverage   65.08%   65.03%   -0.05%     
==========================================
  Files         473      473              
  Lines       23620    23623       +3     
  Branches     3353     3353              
==========================================
- Hits        15372    15364       -8     
- Misses       7047     7057      +10     
- Partials     1201     1202       +1     

Files Changed	Coverage Δ
packages/core/src/Engine.ts	87.21% <ø> (-0.17%)	⬇️
...ges/core/src/RenderPipeline/BasicRenderPipeline.ts	55.84% <0.00%> (ø)
packages/core/src/Background.ts	52.63% <90.90%> (+4.80%)	⬆️

... and 4 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.