Fix an Unintended Latch

The module selects one 4-bit operand, adds i_carry, then outputs a 5-bit sum.

Behaviour

• i_sel = "00": use i_a;
• i_sel = "01": use i_b;
• i_sel = "10": use i_c;
• i_sel = "11": use 0;
• the circuit must remain fully combinational.

The starter code infers a latch because one case path does not assign the operand. Fix the process without adding a clock.