[accerciser] Restore textview.get_iter_at_location compatibility with earlier gtk

[Samuel Thibault <sthibaul src gnome org>]

commit 8bd85a78ebf49ed2c2c4d3f6449a66ec9f9c1caf
Author: Samuel Thibault <samuel thibault ens-lyon org>
Date:   Mon Jun 10 18:09:42 2019 +0200

    Restore textview.get_iter_at_location compatibility with earlier gtk

 plugins/event_monitor.py | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/plugins/event_monitor.py b/plugins/event_monitor.py
index f6844ea..3865db0 100644
--- a/plugins/event_monitor.py
+++ b/plugins/event_monitor.py
@@ -423,7 +423,10 @@ class EventMonitor(ViewportPlugin):
     '''
     x, y = textview.window_to_buffer_coords(gtk.TextWindowType.WIDGET,
                                              int(event.x), int(event.y))
-    (isText, iter) = textview.get_iter_at_location(x, y)
+    isText = True
+    iter = textview.get_iter_at_location(x, y)
+    if isinstance(iter, tuple):
+        (isText, iter) = iter
     cursor = gdk.Cursor(gdk.CursorType.XTERM)
     if isText:
       for tag in iter.get_tags():