PascalGuenther

Fix a bug where "null" was sent as keyboard markup

1

Only send keyboard markup array if it is not empty

Make video memory volatile

1

gcc at -O3 mightcause crashes otherwise

Fix handling of I2C Errata E302

2

In the original E303 workaround, the application reads `i2c->status`, but compares the result to the interrupt flags. Instead, the bits must be compares against `I2C_STATUS_RXDATAV` and `I2C_STATUS_RXFULL`, respectively