Fix some scan-build issues
Review Request #2554 — Created Aug. 8, 2023 and submitted
finch/gntaccount.c, scan-build thinks that
between the two places it is used; this is not the case, but easiest to
placate it by using a common variable.
finch/gntblist.c, comment out more code to limit dead stores.
pidgin/gtkrequest.c, a non-NULL
initializer is used on a variable that is replaced later by the same thing,
so just initialize to NULL instead.