Consistently use ~empty~ with [[Base]]

spec.html

@@ -4333,6 +4333,7 @@ <h1>HasPrimitiveBase ( _V_ )</h1>
         <p>The abstract operation HasPrimitiveBase takes argument _V_. It performs the following steps when called:</p>
         <emu-alg>
           1. Assert: Type(_V_) is Reference.
+          1. If _V_.[[Base]] is ~empty~, then return *false*.
           1. If Type(_V_.[[Base]]) is either Boolean, String, Symbol, BigInt, or Number, return *true*; otherwise return *false*.
         </emu-alg>
       </emu-clause>
@@ -4342,6 +4343,7 @@ <h1>IsPropertyReference ( _V_ )</h1>
         <p>The abstract operation IsPropertyReference takes argument _V_. It performs the following steps when called:</p>
         <emu-alg>
           1. Assert: Type(_V_) is Reference.
+          1. If _V_.[[Base]] is ~empty~, then return *false*.
           1. If Type(_V_.[[Base]]) is Object or HasPrimitiveBase(_V_) is *true*, return *true*; otherwise return *false*.
         </emu-alg>
       </emu-clause>
@@ -4351,7 +4353,7 @@ <h1>IsUnresolvableReference ( _V_ )</h1>
         <p>The abstract operation IsUnresolvableReference takes argument _V_. It performs the following steps when called:</p>
         <emu-alg>
           1. Assert: Type(_V_) is Reference.
-          1. If _V_.[[Base]] is absent, return *true*; otherwise return *false*.
+          1. If _V_.[[Base]] is ~empty~, return *true*; otherwise return *false*.
         </emu-alg>
       </emu-clause>
 
@@ -7373,7 +7375,7 @@ <h1>GetIdentifierReference ( _env_, _name_, _strict_ )</h1>
         <p>The abstract operation GetIdentifierReference takes arguments _env_ (an Environment Record or *null*), _name_ (a String), and _strict_ (a Boolean). It performs the following steps when called:</p>
         <emu-alg>
           1. If _env_ is the value *null*, then
-            1. Return Reference { [[ReferencedName]]: _name_, [[Strict]]: _strict_ }.
+            1. Return Reference { [[Base]]: ~empty~, [[ReferencedName]]: _name_, [[Strict]]: _strict_ }.
           1. Let _exists_ be ? _env_.HasBinding(_name_).
           1. If _exists_ is *true*, then
             1. Return Reference { [[Base]]: _env_, [[ReferencedName]]: _name_, [[Strict]]: _strict_ }.