T1 firmware update via trezorctl incorrectly throws "Invalid firmware data." if firmware image is too small

[hiviah]

Describe the bug
Updating T1 via trezorctl firmware-update -f trezor.bin throws Invalid firmware data if firmware is too small (I guess less than a full chunk). See attached small sample firmware that just shows trezor logo.

Firmware version and revision
Bootloader must be at least 1.8.0. Revision tested 6ebb388

To Reproduce
Steps to reproduce the behavior:

1. go to bootloader
2. trezorctl firmware-update -f trezor.bin
3. throws Invalid firmware data
4. if you comment out throwing the exception in python/src/trezorlib/firmware.py and try again, the flashing will succeed and firmware will run

Additional context
To create similar small T1 firmware, just put while(1); after oledRefresh in main of trezor.c and build with MEMORY_PROTECT=0

trezor.zip

[matejcik]

fwiw you can use firmware-update --skip-check to side-step the error