Avoid activation failures due to link file errors

[tsangint]

Reproduce step:

// In the project folder's primary directory
touch ln_origin.txt 
ln -s ln_origin.txt ln_linked.txt
rm ln_origin.txt
// open VSCode and activate Dart-Code(Flutter plugin)

If there is a soft link file, but the original file is deleted, fs.statSyncwill throw an error and cause the activation to fail.

[DanTup]

Good spot! Thanks for the fix! 👍