Fix error reporting the wrong line for struct field inits

[mparadinha]

fixes #12752

Before:

parada@sendai ~/r/zig (master)> cat -n error.zig 
     1	const Data = struct {
     2	   p: *u32 = null,
     3	};
     4	
     5	pub fn main() void {
     6	   const d = Data{};
     7	   _ = d;
     8	}
parada@sendai ~/r/zig (master)> zig run error.zig
error.zig:1:14: error: expected type '*u32', found '@TypeOf(null)'
const Data = struct {
             ^~~~~~
referenced by:
    Data: error.zig:1:14
    main: error.zig:6:15
    remaining reference traces hidden; use '-freference-trace' to see all reference traces

Afer:

parada@sendai ~/r/zig (12752)> zig run error.zig
bug_smaller.zig:2:15: error: expected type '*u32', found '@TypeOf(null)'
    p: *u32 = null,
              ^~~~
referenced by:
    Data: bug_smaller.zig:1:14
    main: bug_smaller.zig:6:15
    remaining reference traces hidden; use '-freference-trace' to see all reference traces

[Vexu]

Doing this check for resolveMaybeUndefVal isn't very useful but it should be done before the call to failWithNeededComptime.

[mparadinha]

Would you prefer I wait a bit until #13532 gets merged, and then fix this and rebase?

[Vexu]

There is going to be merge conflicts either way so it doesn't really matter though I'll probably want Andrews opinion on that change so this might be able to get merged first.

[mparadinha]

Didn't have access to my dev machine until now.
Ended up rebasing on master, because #13532 got merged in the meantime.