Append newline to autocomplete input if it's missing (fixes #303)

[MarvinJWendt]

This fixes #303 by appending a newline to the autocomplete file input when it is missing. The fix is tested and seems to work.

[MarvinJWendt]

Offtopic

While browsing trough the code, I found this variable in the same file, which is instantly overwritten:

Maybe worth to remove the first assignment.

[MarvinJWendt]

Test input

This file can be used to test the autocomplete: state.json

It's missing the \n at the end.

Sometimes it's hard to reproduce, as many IDEs put a \n at the end of files automatically when saving (which isn't visible, as only \n\n will create a new visual line).

[antonmedv]

Yes, var is not needed)