window watcher crashes on Chrome Task Manager window

Opening chrome's task manager (shortcut : Shift-Escape), a pop-up appears stating :

> Module aw-watcher-window quit unexpectedly [Restart] [Show details] [Cancel]

Details are

2017-11-21 17:12:57 [INFO ]: Running watcher with poll time 1.0 seconds (aw_watcher_window.main:35)
2017-11-21 17:12:57 [INFO ]: aw-watcher-window has started (aw_watcher_window.main:44)
2017-11-21 17:12:57 [INFO ]: Connection to aw-server established (aw_client.client:281)
2017-11-21 18:10:56 [ERROR]: Exception thrown while trying to get active window: [Errno 5] Input/output error (aw_watcher_window.main:69)

Pressing "restarting" in the notification popup only makes it crash again (with the same details), for so long as the active window is chrome's task manager. If I restart the watcher with an other window being active, it restarts fine and is stable. And crashes right again as soon as the task manager becomes active again (as my mouse goes over
it, as focus follows mouse in my awesome wm).

xprop details

```will@ker:~$ xprop
_NET_WM_STATE(ATOM) =
_NET_WM_DESKTOP(CARDINAL) = 7
_NET_FRAME_EXTENTS(CARDINAL) = 0, 0, 0, 0
WM_STATE(WM_STATE):
window state: Normal
icon window: 0x0
_NET_WM_USER_TIME(CARDINAL) = 2417562315
WM_NORMAL_HINTS(WM_SIZE_HINTS):
program specified location: 1150, 20
program specified minimum size: 460 by 270
WM_NAME(UTF8_STRING) = "Task Manager - Google Chrome"
_NET_WM_NAME(UTF8_STRING) = "Task Manager - Google Chrome"
XdndAware(ATOM) = BITMAP
_MOTIF_WM_HINTS(_MOTIF_WM_HINTS) = 0x2, 0x0, 0x1, 0x0, 0x0
_NET_WM_ICON(CARDINAL) = Icon (64 x 64):

_NET_WM_WINDOW_TYPE(ATOM) = _NET_WM_WINDOW_TYPE_NORMAL
_NET_WM_PID(CARDINAL) = 24459
WM_LOCALE_NAME(STRING) = "en_US.UTF-8"
WM_CLIENT_MACHINE(STRING) = "ker"
WM_PROTOCOLS(ATOM): protocols WM_DELETE_WINDOW, _NET_WM_PING
```