U295 - bones file creation cursing secondary weapon caused panic

As reported, if you're twoweaponing and die, your secondary weapon may
become cursed and drop.  But, the bones file code is dropping everything
and tries to drop it again, causing a panic.  drop_upon_death just clears
things out, so follow suit for uswapwep.

doc/fixes34.2

@@ -2,6 +2,7 @@ $RCSfile$ $Revision$ $Date$
 
 General Fixes and Modified Features
 -----------------------------------
+avoid panic when secondary weapon is cursed while generating bones level
 
 
 Platform- and/or Interface-Specific Fixes

doc/fixes35.0

@@ -3,6 +3,7 @@ $RCSfile$ $Revision$ $Date$
 General Fixes and Modified Features
 -----------------------------------
 setmangry should not be called when a monster enters a bones region
+avoid panic when secondary weapon is cursed while generating bones level
 
 
 Platform- and/or Interface-Specific Fixes

src/bones.c

@@ -124,6 +124,7 @@ struct obj *cont;
 {
 	struct obj *otmp;
 
+	uswapwep = 0; /* ensure curse() won't cause swapwep to drop twice */
 	while ((otmp = invent) != 0) {
 		obj_extract_self(otmp);
 		obj_no_longer_held(otmp);