MAVExplorer Multimonitor support problem

[kd0aij]

Reproduce by dragging a graph window to another monitor, then performing a zoom operation on any graph. Observed on Win10 and Win11; following is from Win11:

Exception in thread Thread-32723:
Traceback (most recent call last):
  File "threading.py", line 932, in _bootstrap_inner
  File "threading.py", line 1254, in run
  File "site-packages\mavproxy-1.8.20-py3.8.egg\MAVProxy\modules\lib\grapher.py", line 465, in xlim_timer
  File "site-packages\mavproxy-1.8.20-py3.8.egg\MAVProxy\modules\lib\grapher.py", line 456, in xlim_change_check
  File "site-packages\matplotlib\backend_bases.py", line 2965, in push_current
  File "site-packages\matplotlib\backend_bases.py", line 2968, in <dictcomp>
  File "site-packages\matplotlib\axes\_base.py", line 831, in get_position
  File "site-packages\matplotlib\axes\_base.py", line 1466, in apply_aspect
  File "site-packages\matplotlib\axes\_base.py", line 873, in _set_position
  File "site-packages\matplotlib\artist.py", line 228, in stale
  File "site-packages\matplotlib\figure.py", line 47, in _stale_figure_callback
  File "site-packages\matplotlib\artist.py", line 228, in stale
  File "site-packages\matplotlib\pyplot.py", line 597, in _auto_draw_if_interactive
  File "site-packages\matplotlib\backends\_backend_tk.py", line 274, in draw_idle
  File "tkinter\__init__.py", line 820, in after_idle
  File "tkinter\__init__.py", line 811, in after
  File "tkinter\__init__.py", line 1519, in _register
RuntimeError: main thread is not in main loop