Sometimes when switching editors, blender crashes. I haven't been able to reproduce this consistently, but happens quite often on my machine always when switching between Python console/Text Editor/3D view

Seems similar to http://projects.blender.org/tracker/?group_id=9&atid=498&func=detail&aid=31465

I have employed the same fix as in r46657 (patch attached), but I still do get crashes from different parts of code.

This is happening on SVN revision r50484

Crash 1:
Program received signal SIGSEGV, Segmentation fault.
0x00000000016020f8 in ED_render_scene_update (bmain=0x7fffe4385748, scene=0x7fffe43f75a8, updated=0) at source/blender/editors/render/render_update.c:102
102 engine = rv3d->render_engine;
(gdb) bt
#0 0x00000000016020f8 in ED_render_scene_update (bmain=0x7fffe4385748, scene=0x7fffe43f75a8, updated=0) at source/blender/editors/render/render_update.c:102
#1 0x0000000001c2a1f9 in dag_editors_scene_update (bmain=0x7fffe4385748, scene=0x7fffe43f75a8, updated=0) at source/blender/blenkernel/intern/depsgraph.c:1768
#2 0x0000000001c2ca86 in DAG_ids_check_recalc (bmain=0x7fffe4385748, scene=0x7fffe43f75a8, time=0) at source/blender/blenkernel/intern/depsgraph.c:2784
#3 0x0000000001c66f4c in BKE_scene_update_tagged (bmain=0x7fffe4385748, scene=0x7fffe43f75a8) at source/blender/blenkernel/intern/scene.c:1043
#4 0x0000000001405524 in wm_event_do_notifiers (C=0x37e49d8) at source/blender/windowmanager/intern/wm_event_system.c:314
#5 0x00000000013f7521 in WM_main (C=0x37e49d8) at source/blender/windowmanager/intern/wm.c:369
#6 0x00000000013efda5 in main ()

Crash 2:
Program received signal SIGSEGV, Segmentation fault.
0x00000000014b2e9e in view3d_main_area_draw (C=0x37e49d8, ar=0x7fffe4ef5928) at source/blender/editors/space_view3d/view3d_draw.c:3164
3164 int draw_border = (rv3d->persp == RV3D_CAMOB && (scene->r.mode & R_BORDER));
(gdb) bt
(gdb) bt
#0 0x00000000014b2e9e in view3d_main_area_draw (C=0x37e49d8, ar=0x7fffe4ef5928) at source/blender/editors/space_view3d/view3d_draw.c:3164
#1 0x00000000018b8b9d in ED_region_do_draw (C=0x37e49d8, ar=0x7fffe4ef5928) at source/blender/editors/screen/area.c:485
#2 0x00000000013f871a in wm_method_draw_overlap_all (C=0x37e49d8, win=0x7fffe556e278, exchange=0) at source/blender/windowmanager/intern/wm_draw.c:271
#3 0x00000000013f9baa in wm_draw_update (C=0x37e49d8) at source/blender/windowmanager/intern/wm_draw.c:776
#4 0x00000000013f752d in WM_main (C=0x37e49d8) at source/blender/windowmanager/intern/wm.c:372
#5 0x00000000013efda5 in main ()
(gdb) print *C->wm.area
$14 = {next = 0x0, prev = 0x0, v1 = 0x7fffe4f06478, v2 = 0x7fffe4f064e8, v3 = 0x7fffe4f96e18, v4 = 0x7fffe4f96e88, full = 0x0, totrct = {xmin = 0,
xmax = 1280, ymin = 0, ymax = 1004}, spacetype = 1 '\001', butspacetype = 1 '\001', winx = 1281, winy = 1005, headertype = 1, pad = 0, do_refresh = 0,
cursor = 0, flag = 9, type = 0x3b14328, spacedata = {first = 0x7fffe4ef5aa8, last = 0x7fffe4e22bc8}, regionbase = {first = 0x7fffe4ef57a8,
last = 0x7fffe4ef5928}, handlers = {first = 0x0, last = 0x0}, actionzones = {first = 0x7fffe4e23888, last = 0x7fffe4f06728}}
(gdb) print *C->wm.region
$15 = {next = 0x0, prev = 0x7fffe4ef57a8, v2d = {tot = {xmin = 0, xmax = 1087, ymin = 0, ymax = 840}, cur = {xmin = 201.915833, xmax = 885.084167,
ymin = 178.921631, ymax = 701.030762}, vert = {xmin = 0, xmax = 0, ymin = 0, ymax = 0}, hor = {xmin = 0, xmax = 0, ymin = 0, ymax = 0}, mask = {
xmin = 0, xmax = 1280, ymin = 0, ymax = 978}, min = {0, 0}, max = {0, 0}, minzoom = 0.00999999978, maxzoom = 1000, scroll = 0, scroll_ui = 0,
keeptot = 1, keepzoom = 3, keepofs = 0, flag = 1024, align = 10, winx = 1281, winy = 979, oldwinx = 1281, oldwiny = 979, around = 0, tab_offset = 0x0,
tab_num = 0, tab_cur = 0, sms = 0x0, smooth_timer = 0x0}, winrct = {xmin = 0, xmax = 1280, ymin = 26, ymax = 1004}, drawrct = {xmin = 0, xmax = 1280,
ymin = 26, ymax = 1004}, winx = 1281, winy = 979, swinid = 3, regiontype = 0, alignment = 0, flag = 0, fsize = 0, sizex = 0, sizey = 0, do_draw = 1,
do_draw_overlay = 0, swap = 0, pad = {0, 0, 0}, type = 0x3b14448, uiblocks = {first = 0x0, last = 0x0}, panels = {first = 0x0, last = 0x0}, handlers = {
first = 0x7fffe50b0f88, last = 0x7fffe498de78}, headerstr = 0x0, regiondata = 0x0}

The root cause seems to be that regiondata is NULL when spacetype = SPACE_VIEW3D, possibly a race condition during view switch - redraw can happen prior to regiondata being set or something like that.