[MERGE #1372 @agarwal-sandeep] Check if script context is closed during RundownSourcesAndReparse
[MERGE #1372 @agarwal-sandeep] Check if script context is closed during RundownSourcesAndReparse

Merge pull request #1372 from agarwal-sandeep:vso6752850

Various calls can go out of engine during rundown and reparse and in between script context can get closed. Tighten the checks in RundownSourcesAndReparse

mrkmarron/ChakraCore,Microsoft/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore,mrkmarron/ChakraCore,mrkmarron/ChakraCore,Microsoft/ChakraCore