TraceWeapon::Activate() client-side asserts on running out of space in active shots array

[mcphedar]

Describe the bug Sometimes with multiple players, a client would see an assert locally on running out of space in TraceWeapon::Activate()

Steps to reproduce Steps to reproduce the behavior:

1. Play a game in MPS with multiple players
2. Observe the assert. This is sporadic and not easily repro'd.