Language Server Crash with Expecting non-empty $root_file_path and $checked_file_path

[tm1000]

See #7246 and psalm/psalm-vscode-plugin#107

Specifically if something crashes deep in Psalm we should try to catch most of these crashes in the language server and continue (if possible). This is one such instance where continuing is fine as the error comes from the result of live typing so the code completion (that is erroring) is wrong as the time of typing the letters.

This is really hard to actually give a code reproduction because it relies on Psalm having a live cache and then that cache changing while live typing. You can see this in the reference issue against psalm-vscode-plugin

See attached PR for resolution: #7247