Unfortunately, it still crashes with the following error. The "Style property "border-top-left-radius" is not gettable" warning may be the culprit.

=================================================================================================
(gnome-tweak-tool:8778): Gtk-CRITICAL **: gtk_widget_get_preferred_height_for_width: assertion `width >= 0' failed

(gnome-settings-daemon:1574): Gtk-WARNING **: Style property "border-top-left-radius" is not gettable

(gnome-settings-daemon:1574): GLib-GObject-WARNING **: gtype.c:4206: type id `0' is invalid

(gnome-settings-daemon:1574): GLib-GObject-WARNING **: can't peek value table for type `<invalid>' which is not currently referenced

(nm-applet:1737): Gtk-WARNING **: Style property "border-top-left-radius" is not gettable

(nm-applet:1737): GLib-GObject-WARNING **: gtype.c:4206: type id `0' is invalid

(nm-applet:1737): GLib-GObject-WARNING **: can't peek value table for type `<invalid>' which is not currently referenced

(notification-daemon:1745): Gtk-WARNING **: Style property "border-top-left-radius" is not gettable

(notification-daemon:1745): GLib-GObject-WARNING **: gtype.c:4206: type id `0' is invalid

(notification-daemon:1745): GLib-GObject-WARNING **: can't peek value table for type `<invalid>' which is not currently referenced
gnome-session[1558]: WARNING: Application 'gnome-settings-daemon.desktop' killed by signal 11

(gnome-tweak-tool:8778): Gtk-WARNING **: Style property "border-top-left-radius" is not gettable
/usr/lib/python2.7/site-packages/gi/types.py:47: Warning: gtype.c:4206: type id `0' is invalid
  return info.invoke(*args, **kwargs)
/usr/lib/python2.7/site-packages/gi/types.py:47: Warning: can't peek value table for type `<invalid>' which is not currently referenced
  return info.invoke(*args, **kwargs)
Window manager warning: Log level 32: Failed to load module "pk-gtk-module"
0.000006: 
0.000117: Failed to load module "pk-gtk-module"
0.001877: cairo-compmgr(ccm_log_print_backtrace+0x1d) [0x805639d]
0.001960: /lib/libglib-2.0.so.0(g_logv+0x219) [0xb6ebfcf9]
0.001976: /lib/libglib-2.0.so.0(g_log+0x34) [0xb6ebfe64]
0.001990: /lib/libgtk-x11-2.0.so.0() [0x4f1fb08b]
0.002004: /lib/libgtk-x11-2.0.so.0() [0x4f1fb43c]
0.002018: /lib/libgtk-x11-2.0.so.0() [0x4f260642]
0.002033: /lib/libgobject-2.0.so.0(g_cclosure_marshal_VOID__PARAM+0xaa) [0xb6fa9d4a]
0.002047: /lib/libgobject-2.0.so.0(+0xbd2e) [0xb6fa5d2e]
0.002061: /lib/libgobject-2.0.so.0(g_closure_invoke+0x197) [0xb6fa6f07]
0.002075: /lib/libgobject-2.0.so.0(+0x1f733) [0xb6fb9733]
0.002089: /lib/libgobject-2.0.so.0(g_signal_emit_valist+0xd50) [0xb6fc2430]
0.002103: /lib/libgobject-2.0.so.0(g_signal_emit+0x34) [0xb6fc25c4]
0.002117: /lib/libgobject-2.0.so.0(+0x118df) [0xb6fab8df]
0.002131: /lib/libgobject-2.0.so.0(g_object_notify+0x180) [0xb6fad670]
0.002145: /lib/libgtk-x11-2.0.so.0() [0x4f263dc4]
0.002159: /lib/libgtk-x11-2.0.so.0(gtk_main_do_event+0x425) [0x4f1da065]
0.002173: /lib/libgdk-x11-2.0.so.0() [0x4f7f8009]
0.002187: /lib/libglib-2.0.so.0(g_main_context_dispatch+0x14b) [0xb6eb80cb]
0.002201: /lib/libglib-2.0.so.0(+0x47470) [0xb6eb8470]
0.002215: /lib/libglib-2.0.so.0(g_main_loop_run+0x83) [0xb6eb88d3]
0.002229: /lib/libgtk-x11-2.0.so.0(gtk_main+0xb0) [0x4f1d8c60]
0.002243: cairo-compmgr(main+0x1ba) [0x805587a]
0.002257: /lib/libc.so.6(__libc_start_main+0xf5) [0xb6cd2635]
0.002271: cairo-compmgr() [0x80559b9]
Gtk-Message: Failed to load module "pk-gtk-module"
Gtk-Message: Failed to load module "pk-gtk-module"
Gtk-Message: Failed to load module "pk-gtk-module"
Gtk-Message: Failed to load module "pk-gtk-module"
Gtk-Message: Failed to load module "pk-gtk-module"
Gtk-Message: Failed to load module "pk-gtk-module"

(gnome-settings-daemon:8788): Gtk-WARNING **: Style property "border-top-left-radius" is not gettable

(gnome-settings-daemon:8788): GLib-GObject-WARNING **: gtype.c:4206: type id `0' is invalid

(gnome-settings-daemon:8788): GLib-GObject-WARNING **: can't peek value table for type `<invalid>' which is not currently referenced
gnome-session[1558]: WARNING: App 'gnome-settings-daemon.desktop' respawning too quickly
gnome-session[1558]: WARNING: Application 'gnome-settings-daemon.desktop' killed by signal 11
Gtk-Message: Failed to load module "pk-gtk-module"