menu.inc: fix PHP warning on Arid planets
menu.inc: fix PHP warning on Arid planets

Since Arid planets lack a "Financial" page, we were getting
an undefined index when we queried the `$planetOptions`.

However, `$planet->getOptions(...)` takes care of the check
for existence of the index (and it is cached), so it is an
obvious drop-in replacement that fixes the PHP warning.

hemberger/smr,hemberger/smr,smrealms/smr,hemberger/smr,smrealms/smr,smrealms/smr,hemberger/smr