[ide] misconfigured emiter in vscode won't be reported in vscode and it will also block the linter rules to run silently

[RodgeFu]

repro:

1. write some valid typespec and config an invalid emitter
2. No issue is reported in vscode about the invalid emitter
3. configure some linter rule
4. the linter won't take effect because the compile stopped for the invalid emitter. And there is no error shown in the vscode which tells user everything is good which is incorrect.

expected:
error reported for the invalid emitter