Fix check not updated when fetch package errors

When a package was removed from AUR, the check code didn't update the last_check
value and the loop code was always triggered.

[DEBUG] Next check is planned in -778781s, waiting for 1s
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[DEBUG] Next check is planned in -778781s, waiting for 1s
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[DEBUG] Next check is planned in -778781s, waiting for 1s
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[DEBUG] Next check is planned in -778781s, waiting for 1s
2 jobs for master in 11 minutes and 7 seconds (queued for 23 seconds)
latest
Status Job ID Name Coverage
  Build
passed #489
makepkg

00:00:16

 
  Deploy
passed #490
commitpkg

00:10:50