[MERGE #994] MSFT: 7563889 stress AV when javascriptLibrary is nullptr
[MERGE #994] MSFT: 7563889 stress AV when javascriptLibrary is nullptr

Merge pull request #994 from Yongqu:bugfixs
JavascriptLibrary can null be if the script context initialization threw.
move the cleanup code inside the null check block.

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