Issues/60

[Matyrobbrt]

Pull Request

Pull Request Checklist

• [x] I have checked the pull request page for upcoming or merged features/bug fixes.
• [x] I have read JDA's contributing guidelines.

Pull Request Information

Check and fill in the blanks for all that apply:

• [x] My PR fixes a bug, error, or other issue with the library's codebase.
• [x] My PR is for the command module of the JDA-Utilities library.
• [ ] My PR creates a new module for the JDA-Utilities library: ____.

Description

Currently, CommandClientImpl#getParts always expects a space after a mention, and such, it crashes with a StringIndexOutOfBoundsException when the message is just a ping. This PR fixes that by checking the length of the string before continuing.

Closes #60