Describe the bug
I couldn't decide if this was a languageserver issue or not, sorry. Every time I open a new file, the top line shows the error Failed to run diagnostics: lintr.

Expected behavior
I expect the files lints to be correctly checked and any issues display in the problems tab.

Environment (please complete the following information):

• OS: macOS
• Version: 1.45.1
  Commit: 5763d909d5f12fe19f215cbfdd29a91c0fa9208a
  Date: 2020-05-14T08:33:47.663Z
  Electron: 7.2.4
  Chrome: 78.0.3904.130
  Node.js: 12.8.1
  V8: 7.8.279.23-electron.0
  OS: Darwin x64 19.4.0
• R Version: 3.6.3
• vscode-R version: 1.3.0
• languageserver version: 0.3.5
• lintr version: 2.0.1

Additional context
I see the following in the diagnostics but I am not sure if it is related.

diagnostics_task: <callr_status_error: callr subprocess failed: attempt to apply non-function>
 in process 
-->
<callr_remote_error in linters[[linter]](expr):
 attempt to apply non-function>
 in process 78394 

I know this is all very vague, please let me know if you need any additional information.