sqf: fix serilizing empty code

[PabstMirror]

maybe alt to #754
I think we still need #748 for extracting vars that are single chars

cba/ace builds using this seem to work fine, but I don't have full confidence

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 1 line in your changes missing coverage. Please review.

Project coverage is 65.2%. Comparing base (0981a02) to head (b7d9d96).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
libs/sqf/src/compiler/mod.rs	66.6%	1 Missing ⚠️

Additional details and impacted files

Files with missing lines	Coverage Δ
libs/sqf/src/compiler/mod.rs	97.2% <66.6%> (-0.5%)	⬇️

... and 1 file with indirect coverage changes

[BrettMayson]

Using this branch I don't see any of the issues that #736 fixed for us