You seem to take not care of proper indention in your code.
The compiler does not care about indention But you should.
simply press Ctrl-T to autoformat your code to the correct indentions
If your RFID is sending a single byte this means
RFID1.available()
results in true
not sure if this helps
If you do not use a while-loop but instead a code like shown in
Be the change you want to see in the world
best regards Stefan