Fixes compiler warnings in pktriggercord-cli.c

[sh0]

This PR consists of two commits fixing two different issues.

Commits:

• This commit adds casts where -1 is compared to enum values. This will quiet compiler warnings about signed-unsigned compares and also make sure comparisons are done in the way intended.
• Changes variable 'i' to unsigned type to quiet signed-unsigned compare warning. The variable is only in 'for' loops already in unsigned comparison mode so there are no code behavior changes.

Again, I have no way of testing the changes, but they are fairly straightforward.

[asalamon74]

Thanks, committed.