make share only if files exist.

[xibr]

This pull request fixes issue #167 where files are checking if they exist before the share menu is opened, if the file or files are missing or deleted returns an error message.

Pre-launch Checklist

• [x] I read the Contributor Guide and followed the process outlined there for submitting PRs.
• If you made changes to the code:
  • [ ] I added new tests to check the change I am making or feature I am adding.
  • [ ] All existing and new tests are passing.

[proninyaroslav]

Thank you.