Fix race condition on error fetching

Sometimes the appropriate buffer was determined using the
minibuffer as the filename, which resulted an error. This
guards the overlay printing

The communication should include which filename the errors
are for to avoid this kind of issue in the future.
Commit for discussion
Removed FSharpLocalResolveResult
Merge pull request #17 from 7sharp9/tooltip-changes

Removed FSharpLocalResolveResult
Merge pull request #289 from rneatherway/tooltip-changes

Tooltip changes