Filesystem-int delete non-existing file fix

[coltonmercurio]

Fix odd case where the VM would quickly create a file then delete it. Race condition where the browser filesystem does not have enough time to create a local file before the VM notifies the browser file system to delete it. Fixed by null checking and re-ordering logic.

[neelabhg]

Changes look good to me, although I'm not familiar with the filesystem implementation very much (in case you were waiting on my review)