Should not display mode change for added file that is executable

[kuychaco]

Clicking "Stage Mode Change" causes an error:

Uncaught (in promise) GitError: git -c color.ui=false -c color.status=false -c color.showBranch=false -c color.diff=false -c color.branch=false update-index --cacheinfo 100755,<OID_TBD>,exec in /Users/kuychaco/src/test-repo exited with code 129
stdout: 
stderr: 14:59:26.272274 git.c:344               trace: built-in: git 'update-index' '--cacheinfo' '100755,,exec'
error: option 'cacheinfo' expects <mode>,<sha1>,<path>
    at new GitError (/Users/kuychaco/github/github/lib/git-shell-out-strategy.js:32:18)
    at /Users/kuychaco/github/github/lib/git-shell-out-strategy.js:272:23
    at Generator.next (<anonymous>)
    at step (/Users/kuychaco/github/github/lib/git-shell-out-strategy.js:20:1)
    at /Users/kuychaco/github/github/lib/git-shell-out-strategy.js:20:1
    at <anonymous>