Undefining a structure member sometimes causes the related expression to have a wrong type

#include <stdio.h>
#include <inttypes.h>
#include <stdbool.h>

struct B
{
    uint64_t a;
    bool b;
    uint64_t c;
};

struct B b;

int main()
{
    b.b = true;
    b.c = 0x12345678;
    return 0;
}

I got some correct output like this:

>>> current_mlil[1]
<il: [0x4030].q = 0x12345678>
>>> current_mlil[1].operands
[<il: 0x4030>, <il: 0x12345678>]
>>> current_mlil[1].operands[1].expr_type
<type: uint64_t>

Then if I go to type view and undefine the member c of the struct B, the expr_type changes and it is wrong:

>>> current_mlil[1].operands[1].expr_type
<type: struct B>

I am really expecting the expr_type go back to void, which was the type of before I apply the type of struct B.

Start with the supplied C reproducer and inspect current_mlil[1].operands[1].expr_type before and after undefining member c in the type view. Trace how the undefinition updates the related MLIL expression and verify that the operand type returns to void rather than struct B.