[Freeciv-Dev] (PR#4769) memory error with disbanded city

["Jason Short" <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

Looks like if a city is disbanded because of producing settlers, the 
end-of-turn update continues running on that city.

==6512== Invalid read of size 4
==6512==    at 0x806CB60: city_distribute_surplus_shields (cityturn.c:916)
==6512==    by 0x806D5DD: city_build_stuff (cityturn.c:1141)
==6512==    by 0x806DD2E: update_city_activity (cityturn.c:1366)
==6512==    by 0x806BC16: update_city_activities (cityturn.c:414)
==6512==    by 0x804E732: end_turn (srv_main.c:501)
==6512==    by 0x804FF52: main_loop (srv_main.c:1508)
==6512==    by 0x80502F4: srv_main (srv_main.c:1591)
==6512==    by 0x804A007: main (civserver.c:154)
==6512==    by 0x403A04EC: __libc_start_main (in /lib/libc-2.3.2.so)
==6512==    by 0x8049C60: (within /tmp/jshort/freeciv/server/civserver)
==6512==    Address 0x42E9DFE4 is 188 bytes inside a block of size 2124 
free'd
==6512==    at 0x40160A1F: free (vg_clientfuncs.c:185)
==6512==    by 0x80ACA34: game_remove_city (game.c:182)
==6512==    by 0x8068807: remove_city (citytools.c:1161)
==6512==    by 0x806CBD1: city_distribute_surplus_shields (cityturn.c:921)
==6512==    by 0x806D5DD: city_build_stuff (cityturn.c:1141)
==6512==    by 0x806DD2E: update_city_activity (cityturn.c:1366)
==6512==    by 0x806BC16: update_city_activities (cityturn.c:414)
==6512==    by 0x804E732: end_turn (srv_main.c:501)
==6512==    by 0x804FF52: main_loop (srv_main.c:1508)
==6512==    by 0x80502F4: srv_main (srv_main.c:1591)
==6512==    by 0x804A007: main (civserver.c:154)
==6512==    by 0x403A04EC: __libc_start_main (in /lib/libc-2.3.2.so)
==6512==    by 0x8049C60: (within /tmp/jshort/freeciv/server/civserver)

Followed by dozens of other related messages.

jason