LibWasm+LibWeb: Allow tables to have externrefs in the JS API

Author: https://github.com/dzfrias
Commit: 4e7d3026d2
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/1105
Reviewed-by: https://github.com/alimpfard

Userland/Libraries/LibWasm/AbstractMachine/AbstractMachine.h

@@ -74,9 +74,25 @@ private:
 
 class Value {
 public:
-    Value()
+    explicit Value(ValueType type)
         : m_value(u128())
     {
+        switch (type.kind()) {
+        case ValueType::I32:
+        case ValueType::I64:
+        case ValueType::F32:
+        case ValueType::F64:
+        case ValueType::V128:
+            break;
+        case ValueType::FunctionReference:
+            // ref.null funcref
+            m_value = u128(0, 2);
+            break;
+        case ValueType::ExternReference:
+            // ref.null externref
+            m_value = u128(0, 3);
+            break;
+        }
     }
 
     template<typename T>