Use zero as unused entry ref as that matches an invalid entry ref.
The previous value was within the range of valid entry refs and we could (very rarely) consider a set entry ref to not being set.
@@ -25,7 +25,7 @@ struct ChangeBase {
DIV,
CLEARDOC
};
- enum {UNSET_ENTRY_REF = 0xffffffffu};
+ enum {UNSET_ENTRY_REF = 0};
ChangeBase() :
_type(NOOP),
