Minor tweaks/fixes for the Command Palette

[YeldhamDev]

Had the wish for these changes to be made, but didn't want to keep bothering the student. So I just waited so I could do them myself.

• Fix first section being hidden by being scrolled up on popup.
• Made sections non-selectable. This prevents the dialog from trying to open a command with it, resulting in an error message.
• Took the time to also disable selecting the sections in the shortcut tab in the Editor Settings as well.
• Removed the "No matches found" when no commands are found given the search string. It implementation felt hacky, and I honestly don't feel it was really needed.
• General code tidy up.

[akien-mga]

CC @Bhu1-V

[EricEzaM]

Noice

[akien-mga]

Thanks!