Fix resuming when child has errored (WIP)

[rowanseymour]

Should fix https://sentry.io/organizations/nyaruka/issues/1540872681/?project=227973&referrer=alert_email

Still trying to figure out a way to test this

[codecov[bot]]

Codecov Report

Merging #879 into master will decrease coverage by <.01%. The diff coverage is 75%.

@@            Coverage Diff             @@
##           master     #879      +/-   ##
==========================================
- Coverage   85.48%   85.47%   -0.01%     
==========================================
  Files         220      220              
  Lines       11226    11226              
==========================================
- Hits         9596     9595       -1     
- Misses       1223     1224       +1     
  Partials      407      407

Impacted Files	Coverage Δ
flows/engine/session.go	69.23% <100%> (ø)	:arrow_up:
flows/runs/run.go	78.09% <50%> (-0.42%)	:arrow_down:

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