Issue with modified A1 example code

[Slanderkin]

I have modified (code here) the A1 lidar example to use another python lidar api for the YDLIDAR. In the call:

if not viz.display(x/1000., y/1000., theta, mapbytes): exit(0)

my code crashes. I used fault handler to attempt to narrow down the location of the issue and got the following back:

`Fatal Python error: Segmentation fault

Current thread 0xb6fbfad0 (most recent call first):
File "/home/pi/.local/lib/python3.7/site-packages/matplotlib/image.py", line 567 in _make_ima ge
File "/home/pi/.local/lib/python3.7/site-packages/matplotlib/image.py", line 927 in make_imag e
File "/home/pi/.local/lib/python3.7/site-packages/matplotlib/image.py", line 642 in draw
File "/home/pi/.local/lib/python3.7/site-packages/matplotlib/artist.py", line 41 in draw_wrap per
File "/home/pi/.local/lib/python3.7/site-packages/matplotlib/image.py", line 131 in _draw_lis t_compositing_images
File "/home/pi/.local/lib/python3.7/site-packages/matplotlib/axes/_base.py", line 2747 in dra w
File "/home/pi/.local/lib/python3.7/site-packages/matplotlib/cbook/deprecation.py", line 411 in wrapper
File "/home/pi/.local/lib/python3.7/site-packages/matplotlib/artist.py", line 41 in draw_wrap per
File "/home/pi/.local/lib/python3.7/site-packages/matplotlib/image.py", line 131 in _draw_lis t_compositing_images
File "/home/pi/.local/lib/python3.7/site-packages/matplotlib/figure.py", line 1864 in draw
File "/home/pi/.local/lib/python3.7/site-packages/matplotlib/artist.py", line 41 in draw_wrap per
File "/home/pi/.local/lib/python3.7/site-packages/matplotlib/backends/backend_agg.py", line 4 07 in draw
File "/home/pi/.local/lib/python3.7/site-packages/matplotlib/backends/backend_tkagg.py", line 9 in draw
File "/home/pi/.local/lib/python3.7/site-packages/matplotlib/backends/_backend_tk.py", line 2 53 in idle_draw
File "/usr/lib/python3.7/tkinter/init.py", line 749 in callit
File "/usr/lib/python3.7/tkinter/init.py", line 1705 in call
File "/usr/lib/python3.7/tkinter/init.py", line 1177 in update
File "/home/pi/.local/lib/python3.7/site-packages/matplotlib/backends/_backend_tk.py", line 3 90 in flush_events
File "/home/pi/.local/lib/python3.7/site-packages/matplotlib/backend_bases.py", line 2407 in start_event_loop
File "/home/pi/.local/lib/python3.7/site-packages/matplotlib/pyplot.py", line 438 in pause
File "/usr/local/lib/python3.7/dist-packages/roboviz/init.py", line 156 in _refresh
File "/usr/local/lib/python3.7/dist-packages/roboviz/init.py", line 193 in display
File "slamTest.py", line 100 in
Segmentation fault
`
Any idea on how I can fix this issue? I don't believe the fault lies with the ydlidar code as I've used nearly identical code on its own with no problems.