Should the display be cleared when trying to print an invalid character?

[microbit-carlos]

For example uBit.display.print("Hi O갎o") displays the O character 4 times in a row (갎 is 0xEA 0xB0 0x8E in UTF-8, which I can confirm is what I see compiled in the code). It does not blink, it's just permanently shown for 4x the animation time.

This is because when a character is "printed" on the display, it uses the image buffer in the display instance to render the character using Image::print(), which exits early if the character is out-of-range and doesn't change the image:
codal-core/source/types/Image.cpp#L578

So, when printing "Hi O갎o", it shows O for 4 iterations.

The change would be simple, in AnimatedDisplay::updatePrintText() we could check the return value from Image::print() and clear the display if the return is DEVICE_INVALID_PARAMETER:
codal-core/source/drivers/AnimatedDisplay.cpp#L182

This would align a bit more with what uBit.display.scroll() currently does, but it would be considered a change in behaviour (V1 and V2 do the same now), so maybe we might not want to change this.