load can lead to program exiting

[sogaiu]

Description: Answering "yes" to a prompt that comes up while attempting the load command when one's buffer has been modified can lead to the program exiting.

Expectation: The requested file be loaded and displayed and the editor remain running :)

Steps to reproduce follow.

---

At shell:

$ cd joule
$ janet src/joule.janet project.janet

In editor:

• Make some change -- e.g. type space followed by backspace
• Ctrl-L to load another file
• Type a path, say, src/joule.janet
• Answer "yes" to Are you sure? Unsaved changes will be lost. (yes/No/save)

Observe being back at shell prompt, then:

$ echo $?
1

Scroll back up to see:

$ janet src/joule.janet project.janet 
error: could not find method :+ for nil
  in inc [boot.janet] on line 148, column 32
  in update [boot.janet] on line 1520, column 15
  in edup [src/joule.janet] (tailcall) on line 77, column 11
  in editor-scroll [src/joule.janet] on line 202, column 11
  in editor-refresh-screen [src/joule.janet] on line 451, column 34
  in <anonymous> [src/joule.janet] on line 1148, column 17
  in <anonymous> [src/joule.janet] on line 1151, column 16
  in main [src/joule.janet] (tailcall) on line 1145, column 3
  in run-main [boot.janet] on line 3783, column 16
  in cli-main [boot.janet] on line 3928, column 17

The environment here was:

• Linux box
• joule-editor 60d258c
• janet 1.26.0-dev-a8a78d45

[CFiggers]

Replicated! I'll probably address this as part of v0.0.5.

Thanks for reporting!