gSheets query - 'non required' multiple dropdowns

[dmj120]

I have a nice query function that works when BOTH C2 and C3 are selected (via dependent dropdowns).

However, I really need it to not "require" C3. I've tried AND (below), as well as OR, but I cannot get it to work.

Any thoughts???

=QUERY('System Inv 7.19'!A2:AP, "select C,D,E,F,W,X,AL,AN,AO,AP where A = """&C2&""" AND B = """&C3&""" order by B",1)