LibJS: Use empty value for Reference unresolvable state, not undefined

This fixes an issue where `undefined.foo = "bar"` would throw a
ReferenceError instead of a TypeError as undefined was also used for
truly unresolvable references (e.g. `foo() = "bar"`). I also made the
various error messages here a bit nicer, just "primitive value" is not
very helpful.

1 files changed, 2 insertions, 2 deletions

diff --git a/Userland/Libraries/LibJS/Runtime/Reference.h b/Userland/Libraries/LibJS/Runtime/Reference.h
index d5a8010916..ff94bd0359 100644
--- a/Userland/Libraries/LibJS/Runtime/Reference.h
+++ b/Userland/Libraries/LibJS/Runtime/Reference.h
@@ -64,7 +64,7 @@ public:
     const PropertyName& name() const { return m_name; }
     bool is_strict() const { return m_strict; }
 
-    bool is_unresolvable() const { return m_base.is_undefined(); }
+    bool is_unresolvable() const { return m_base.is_empty(); }
     bool is_property() const
     {
         return m_base.is_object() || has_primitive_base();
@@ -91,7 +91,7 @@ public:
 private:
     void throw_reference_error(GlobalObject&);
 
-    Value m_base { js_undefined() };
+    Value m_base;
     PropertyName m_name;
     bool m_strict { false };
     bool m_local_variable { false };