Actually, I think I was wrong, it's an issue in the Zathras weapons.tbl, not the TBP weapons.tbl. I've attached a fix, and see the diff below for when the attachment is deleted:
--- /tmp/weapons.tbl 2016-02-14 16:17:33.225262534 +1000
+++ data/tables/weapons.tbl 2016-02-14 16:15:28.313261701 +1000
@@ -7542,6 +7542,7 @@
+Start Alpha: 0.0
+End Alpha: 0.0
+Max Life: 0.0
+ +Bitmap: EAmissile3
$Icon: iconTempest
$Anim: Tempest
$Impact Explosion Radius: 0.0
(only thing is, I'm sure I tried to fix this without success ages ago, so I'm really confused if the fix is this simple, my past self must have been on drugs or something...)
[attachment DELETED!! by Strong Bad]