prevent await blocks using stale state

[Rich-Harris]

fixes #1131

[codecov-io]

Codecov Report

Merging #1150 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1150   +/-   ##
=======================================
  Coverage   91.48%   91.48%           
=======================================
  Files         126      126           
  Lines        4524     4524           
  Branches     1461     1461           
=======================================
  Hits         4139     4139           
  Misses        163      163           
  Partials      222      222

Impacted Files	Coverage Δ
src/generators/nodes/AwaitBlock.ts	94.28% <ø> (ø)	⬆️

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