Crash on active weapon == -1

[fokkonaut]

In F-DDrace you can drop weapon using F4. In combination with DDNet's ability to show no weapon at all (-1) this crashes TaterClient.

Reported by XaRTeCK / Probablement.

TClient/src/game/gamecore.cpp

Line 65 in 4e42693

default: dbg_assert_failed("invalid weapon");