Check if flight or flight.info is not nil. Without this check a panic then subsequent deadlock can occur
Merge pull request #179 from ChannelMeter/fix-batch-deadlock-nil-access

executeBatch can cause a dead lock to a nil deref causing c.prepMu not to be unlocked.
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Addressed reviewer's remarks
Minor formatting tweaks
Fixed a few typos
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Merge pull request #182 from relops/contributions

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