[nanoleaf] Bugfix: Handle non-integer panel ids (#13951)

[nanoleaf] Bugfix: Handle non-integer panel ids (#13951)

Panel ids are sometimes returned as BigInteger

We haven't been able to understand why this happens somewhere and
somewhere not, but this is an sledgehammer attempt to fix it quickly
to unblock users, and then we will try to understand it later.

Discussions:
https://community.openhab.org/t/java-lang-classcastexception-class-java-math-bigdecimal-cannot-be-cast-to-class-java-lang-integer/142035/16
https://community.openhab.org/t/nanoleaf-binding-oh3-stabilization-update/116300/61

Signed-off-by: Jørgen Austvik <jaustvik@acm.org>