Fixes for allowing :throw_undef_if_not on the frontend

[Pangoraw]

#53875 allowed :throw_undef_if_not as a frontend form.

However, the UndefVarError being tested is thrown because the first argument is resolved to a global ref:

julia> @eval function has_tuin()
           $(Expr(:throw_undef_if_not, :x, false))
       end
has_tuin (generic function with 1 method)

julia> @code_lowered has_tuin() # master
CodeInfo(
1 ─ %1 = $(Expr(:throw_undef_if_not, :(Main.x), false))
└──      return %1
)

julia> @code_lowered has_tuin() # this pr
CodeInfo(
1 ─ %1 = $(Expr(:throw_undef_if_not, :x, false))
└──      return %1
)

This change skips this global ref resolution for the first argument and fixes a typo which would throw an error in case of non-const second argument.

[Keno]

Good catch, thanks