py: Fix version header generation when no tags are available.
py: Fix version header generation when no tags are available.

adafruit/micropython,adafruit/circuitpython,adafruit/circuitpython,adafruit/micropython,adafruit/circuitpython,adafruit/micropython,adafruit/micropython,adafruit/circuitpython,adafruit/circuitpython,adafruit/circuitpython,adafruit/micropython