frontend: fix wrong result of Value.getFunction

Fixes regression introduced in
db33ee45b7261c9ec62a1087cfc9377bc4e7aa8f.

Found from compiling bun. Unfortunately we do not have a behavior test
reduction for this bug.
076b54c8e7Andrew Kelley committed on 7/23/2023, 2:57:23 AMparent1ae839c
1 file changedLine totals unavailable