POP: Don't allow F.low to be set

src/cpu.rs

@@ -624,6 +624,9 @@ mod instructions {
         }
         pub fn insn_pop(&mut self, reg: R16Stack, bus: &mut impl BusIO) -> IResult {
             self[reg].0 = self.pop16(bus)?;
+            if let R16Stack::AF = reg {
+                self.af.wide_mut().0 &= 0xfff0; // lo flags should never be set
+            }
             Ok(())
         }
     }