Fix #17549: Prevent MIDI KeyUp-event from executing mapped command

[niklas-simon]

Resolves: #17549

When mapping a command to a MIDI button, the command is executed both for press and release. This PR fixes the issue by checking the velocity of the button press.

• I signed the CLA
• The title of the PR describes the problem it addresses
• Each commit's message describes its purpose and effects, and references the issue it resolves
• If changes are extensive, there is a sequence of easily reviewable commits
• The code in the PR follows the coding rules
• There are no unnecessary changes
• The code compiles and runs on my machine, preferably after each commit individually
• I created a unit test or vtest to verify the changes I made (if applicable)