Numerous "255 not found in table 4.5" errors from UPP

[SamuelTrahanNOAA]

The UPP generates messages like this, both in the offline post and inline post:

get_g2_fixedsurfacetypes key: 255 not found in table 4.5

It turns out this is a special case of a broader problem in UPP:

• UPP sends invalid empty keys to g2tmpl, and g2tmpl lacks proper error handling #977

All these errors come from fields without fixed_sfc2_type. The correct solution is to assign fixed_sfc1_type to fixed_sfc2_type, since that's the behavior UPP has had since time immemorial. It turns out it had that behavior due to two bugs, but we can make the behavior is explicit and bug-free.