123213

### How did it happen?
1.
2.
3.

### Error log

```
EISDIR: illegal operation on a directory, read '/Users/chenchen/Desktop/haibang-ui/.exportedArtboards/rui/Checkbox '

{
"path": "/Users/chenchen/Desktop/haibang-ui/.exportedArtboards/rui/Checkbox ",
"syscall": "read",
"code": "EISDIR",
"errno": -21
}

o@/Users/chenchen/Library/Application Support/com.bohemiancoding.sketch3/Plugins/Git.sketchplugin/Contents/Sketch/__commands_Commit.js:1:28692
@/Users/chenchen/Library/Application Support/com.bohemiancoding.sketch3/Plugins/Git.sketchplugin/Contents/Sketch/__commands_Commit.js:1:29167
@/Users/chenchen/Library/Application Support/com.bohemiancoding.sketch3/Plugins/Git.sketchplugin/Contents/Sketch/__commands_Commit.js:1:5357
@/Users/chenchen/Library/Application Support/com.bohemiancoding.sketch3/Plugins/Git.sketchplugin/Contents/Sketch/__commands_Commit.js:1:34549
forEach@[native code]
b@/Users/chenchen/Library/Application Support/com.bohemiancoding.sketch3/Plugins/Git.sketchplugin/Contents/Sketch/__commands_Commit.js:1:34463
@/Users/chenchen/Library/Application Support/com.bohemiancoding.sketch3/Plugins/Git.sketchplugin/Contents/Sketch/__commands_Commit.js:1:35882
@/Users/chenchen/Library/Application Support/com.bohemiancoding.sketch3/Plugins/Git.sketchplugin/Contents/Sketch/__commands_Commit.js:1:35374
@/Users/chenchen/Library/Application Support/com.bohemiancoding.sketch3/Plugins/Git.sketchplugin/Contents/Sketch/__commands_Commit.js:1:35407
__skpm_run@/Users/chenchen/Library/Application Support/com.bohemiancoding.sketch3/Plugins/Git.sketchplugin/Contents/Sketch/__commands_Commit.js:1:36220
__skpm_run@[native code]
```

Start with the Sketch plugin stack trace in __commands_Commit.js and the reported EISDIR path under .exportedArtboards. Reproduce the commit flow with a directory at that path and trace how the plugin handles it. Done means the commit flow no longer attempts an invalid directory read and the behavior is verified against this error.

Written by the indexing model from the issue text.