1) Launch -> Evolution
2) Goto "Calendars" -> Click "New" button above
3) When "Appointment" dialog pop-up -> Click on "Alarm" button.
4) When "Alarm" dialog pop-up -> Click on "Alarm" drag-down button
5) Choose "Customize" -> Click on new created action/trigger
6) Click on "Edit" button.

Expected Result: An "Edit Trigger" dialog pop-up.

Actual Result: Evolution crash.

Stacktrace:

gtk-critical **: file gtktextbuffer.c: line 551: assertion 'text != NULL' failed.

[1] _waitid(0x0, 0x630, 0x8045db0, 0x3), at 0xce709a25
  [2] _waitpid(0x630, 0x8045ec4, 0x0), at 0xce6d577f
  [3] waitpid(0x630, 0x8045ec4, 0x0), at 0xce6fd107
  [4] libgnomeui_segv_handle(0x6, 0x0, 0x8045f70), at 0xd0380aee
  [5] __sighndlr(0x6, 0x0, 0x8045f70, 0xd0380a44), at 0xce7080df
  ---- called from signal handler with signal 6 (SIGABRT) ------
  [6] __lwp_kill(0x1, 0x6), at 0xce7095f5
  [7] _thr_kill(0x1, 0x6), at 0xce705fc9
  [8] raise(0x6), at 0xce6cdfdd
  [9] abort(0x0, 0xcfdce1d4, 0xce7f0eb0, 0xce7013fc, 0x8092168, 0x0), at 0xce6b036f
  [10] g_logv(0xcfdce1d4, 0x8, 0xcfdce854, 0x80466a8), at 0xce7923e4
  [11] g_log(0xcfdce1d4, 0x8, 0xcfdce854, 0xcfdce1f0, 0x227, 0xcfdce80c), at 0xce792411
  [12] gtk_text_buffer_set_text(0x8854318, 0x0, 0xffffffff), at 0xcfcc28fb
=>[13] alarm_to_dalarm_widgets(dialog = 0x8046814, alarm = 0x883fe98), line 368 in "alarm-dialog.c"
  [14] populate_widgets_from_alarm(dialog = 0x8046814), line 618 in "alarm-dialog.c"
  [15] alarm_to_dialog(dialog = 0x8046814), line 252 in "alarm-dialog.c"
  [16] alarm_dialog_run(parent = 0x87ef7f0, ecal = 0x86d1fb0, alarm = 0x883fe98), line 1132 in "alarm-dialog.c"
  [17] edit_clicked_cb(button = 0x87e5e50, data = 0x87b2ed8), line 175 in "alarm-list-dialog.c"
  [18] g_cclosure_marshal_VOID__VOID(0x87f1468, 0x0, 0x1, 0x8046a6c, 0x80469cc, 0x0), at 0xcf69e321
  [19] g_closure_invoke(0x87f1468, 0x0, 0x1, 0x8046a6c, 0x80469cc), at 0xcf68a256
  [20] signal_emit_unlocked_R(0x81e80f0, 0x0, 0x87e5e50, 0x0, 0x8046a6c), at 0xcf69dba0
  [21] g_signal_emit_valist(0x87e5e50, 0xb9, 0x0, 0x8046cd8), at 0xcf69cea5
  [22] g_signal_emit(0x87e5e50, 0xb9, 0x0), at 0xcf69d041
  [23] gtk_button_clicked(0x87e5e50), at 0xcfba1ab9
  [24] gtk_real_button_released(0x87e5e50, 0x80a0858), at 0xcfba2844
  [25] g_cclosure_marshal_VOID__VOID(0x82588a0, 0x0, 0x1, 0x8046ecc, 0x8046e2c, 0xcfba280c), at 0xcf69e321
  [26] g_type_class_meta_marshal(0x82588a0, 0x0, 0x1, 0x8046ecc, 0x8046e2c, 0x1a4), at 0xcf68a551
  [27] g_closure_invoke(0x82588a0, 0x0, 0x1, 0x8046ecc, 0x8046e2c), at 0xcf68a256
  [28] signal_emit_unlocked_R(0x81e80c0, 0x0, 0x87e5e50, 0x0, 0x8046ecc), at 0xcf69d86d
  [29] g_signal_emit_valist(0x87e5e50, 0xb8, 0x0, 0x8047138), at 0xcf69cea5
  [30] g_signal_emit(0x87e5e50, 0xb8, 0x0), at 0xcf69d041
  [31] gtk_button_released(0x87e5e50), at 0xcfba1a49
  [32] gtk_button_button_release(0x87e5e50, 0x813ec1c, 0x80a0530), at 0xcfba26ac
  [33] _gtk_marshal_BOOLEAN__BOXED(0x81ce170, 0x8047270, 0x2, 0x804732c, 0x804728c, 0xcfba2688), at 0xcfc53c9d
  [34] g_type_class_meta_marshal(0x81ce170, 0x8047270, 0x2, 0x804732c, 0x804728c, 0xb4), at 0xcf68a551
  [35] g_closure_invoke(0x81ce170, 0x8047270, 0x2, 0x804732c, 0x804728c), at 0xcf68a256
  [36] signal_emit_unlocked_R(0x8186480, 0x0, 0x87e5e50, 0x80474ac, 0x804732c), at 0xcf69dd65
  [37] g_signal_emit_valist(0x87e5e50, 0x54, 0x0, 0x80475a0), at 0xcf69cc3b
  [38] g_signal_emit(0x87e5e50, 0x54, 0x0, 0x813ec1c, 0x80475c4), at 0xcf69d041
  [39] gtk_widget_event_internal(0x87e5e50, 0x813ec1c), at 0xcfd354de
  [40] gtk_widget_event(0x87e5e50, 0x813ec1c), at 0xcfd3516d
  [41] gtk_propagate_event(0x87e5e50, 0x813ec1c), at 0xcfc52812
  [42] gtk_main_do_event(0x813ec1c, 0x0), at 0xcfc51884
  [43] gdk_event_dispatch(0x80b0380, 0x0, 0x0), at 0xcf8ce03a
  [44] g_main_dispatch(0x80b03c8), at 0xce789ca4
  [45] g_main_context_dispatch(0x80b03c8), at 0xce78ad95
  [46] g_main_context_iterate(0x80b03c8, 0x1, 0x1, 0x80928a8), at 0xce78b1b5
  [47] g_main_loop_run(0x81a0278), at 0xce78b7ba
  [48] bonobo_main(0x80479bc, 0x80478e4, 0xd0ffb840, 0x8047830, 0x80478a0, 0x809936c), at 0xd00bf462
  [49] main(argc = 1, argv = 0x8047928), line 610 in "main.c"


I will provide a patch soon.