Freeciv

Strange behaviour of Lua function (City):inspire_partisans(plr): returns 1 for plr=owner and 0 for other players. Moreover, on certain conditions it makes client to fail. Fragment of console output:

1: in citizens_nation_get() [citizens.c::83]: assertion 'pcity->nationality != ((void *)0)' failed.
2: Backtrace:
2:     0: /opt/freeciv2_6/lib/libfreeciv.so.0(backtrace_print+0x37) [0x7fb4df2fe4e7]
2:     1: /opt/freeciv2_6/lib/libfreeciv.so.0(vdo_log+0x97) [0x7fb4df305707]
2:     2: /opt/freeciv2_6/lib/libfreeciv.so.0(do_log+0xa6) [0x7fb4df3057e6]
2:     3: /opt/freeciv2_6/lib/libfreeciv.so.0(fc_assert_fail+0x14a) [0x7fb4df305aba]
2:     4: /opt/freeciv2_6/lib/libfreeciv.so.0(citizens_nation_get+0xae) [0x7fb4df2171be]
2:     5: /opt/freeciv2_6/bin/freeciv-gtk3(api_methods_city_inspire_partisans+0xbb) [0x55c7d532104b]
2:     6: /opt/freeciv2_6/bin/freeciv-gtk3(+0x142b33) [0x55c7d530ab33]
2:     7: /opt/freeciv2_6/bin/freeciv-gtk3(+0x129c27) [0x55c7d52f1c27]
2:     8: /opt/freeciv2_6/bin/freeciv-gtk3(+0x13895d) [0x55c7d530095d]
2:     9: /opt/freeciv2_6/bin/freeciv-gtk3(+0x129f8f) [0x55c7d52f1f8f]
2:    10: /opt/freeciv2_6/bin/freeciv-gtk3(+0x129fe1) [0x55c7d52f1fe1]
2:    11: /opt/freeciv2_6/bin/freeciv-gtk3(+0x129352) [0x55c7d52f1352]
2:    12: /opt/freeciv2_6/bin/freeciv-gtk3(+0x12a3bb) [0x55c7d52f23bb]
2:    13: /opt/freeciv2_6/bin/freeciv-gtk3(lua_pcallk+0xd5) [0x55c7d52ed185]
2:    14: /opt/freeciv2_6/bin/freeciv-gtk3(luascript_call+0x17f) [0x55c7d52fc49f]
2:    15: /opt/freeciv2_6/bin/freeciv-gtk3(script_client_do_file+0x13) [0x55c7d5242603]
2:    16: /opt/freeciv2_6/bin/freeciv-gtk3(+0x5810d) [0x55c7d522010d]
2:    17: /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0(g_closure_invoke+0x19d) [0x7fb4dd2be10d]
...
2:    34: /opt/freeciv2_6/bin/freeciv-gtk3(_start+0x2a) [0x55c7d52183fa]

Maybe that is because I have taken Mali in editor but it somehow stayed a computer player? That seems wrong but I don't know, that's why I put the bug into Client category.