Harpoon produces error when switching and not in a project

[adurmk1]

While using harpoon and not working in a Project not managed by projectile I encountered an issue when switching files. After executing harpoon-go-to-1 I got this debugger trace:

Debugger entered--Lisp error: (wrong-type-argument stringp nil)
  harpoon--current-file-directory()
  harpoon-project-name-function()
  harpoon--cache-key()
  harpoon--file-name()
  harpoon-go-to(1)
  harpoon-go-to-1()

After a bit of investigating the issue seems to stem from the use of thebuffer-file-name variable in the function harpoon--current-file-directory while being called from within a with-temp-buffer macro inside of the function harpoon-go-to. Inside of harpoon-go-to the function buffer-file-name is also used inside of the with-temp-buffer macro which will probably also cause an error with the file-truename function.

[adurmk1]

this seems to resolve this issue.