Undefined Step Definitions: No longer recognised and "Go To Definition" has regressed (>v2.15.2)

[JTattershall]

Describe the bug
Extension revisions after v2.15.2 are no longer highlighting undefined Step Definitions with the squiggle to indicate they have not been coded.
For those that are undefined, if "Go To Definition" is used, an unrelated page is retrieved instead of stating tooltip.

To Reproduce
Steps to reproduce the behaviour:

1. Be on version >2.15.2
2. On an existing Feature file, add a new definition that does not yet exist.
3. A squiggly line no longer appears to indicate no associated code block for that definition was found.
4. "Go To Definition" on that definition previously would display a tooltip stating definition not found, now a seemingly random code page is shown from the project library.

Expected behaviour

1. Undefined step definitions would highlight with a squiggly line to indicate they are not yet coded.
2. Hover-over step and "Go To Definition" would provide tooltip regarding definition not found.

Screenshots
If applicable, add screenshots to help explain your problem.

1. Previous behaviour of undefined definitions:
   

2. Previous tooltip behaviour
   
   

Additional details:

May be related to existing case: #493

Step definition:
If applicable, add example of step definition:

When This step is not real it should underline