[MERGE #6224 @zenparsing] Fix assertion in ArrayBuffer slice
[MERGE #6224 @zenparsing] Fix assertion in ArrayBuffer slice

Merge pull request #6224 from zenparsing:arraybuffer-slice-assert

Fixes #6220

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