I did not reproduce the exact problem reported; however, I reproduced
that a failure to construct an RGBMatrix object would leave CircuitPython
in an inconsistent state with a display bus registered but not working:
```py
>>> import rgbmatrix, board; rgbmatrix.RGBMatrix(width=64, bit_depth=1, rgb_pins=[], addr_pins=[], clock_pin=board.A0, latch_pin=board.A1, output_enable_pin=board.A2)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: The length of rgb_pins must be 6, 12, 18, 24, or 30
>>> import rgbmatrix, board; rgbmatrix.RGBMatrix(width=64, bit_depth=1, rgb_pins=[], addr_pins=[], clock_pin=board.A0, latch_pin=board.A1, output_enable_pin=board.A2)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
RuntimeError: Too many display busses; forgot displayio.release_displays() ?
```
After the fix the second call also results in a ValueError, not a
RuntimeError, which is correct.
Closes#9674
Jeff Epler
ed5c0bd465