LibJS: Return the allocated dst register from deleting super properties

Even though calling delete on a super property will ultimately throw a
ReferenceError, we must return the allocated register for the result of
the delete operation (which would normally be a boolean). If the delete
operation is used in a return statement, the bytecode generator for the
return statement must be able to assume the statement had some output.

Libraries/LibJS/Bytecode/Generator.cpp

@@ -812,7 +812,7 @@ CodeGenerationErrorOr<Optional<ScopedOperand>> Generator::emit_delete_reference(
                 emit<Bytecode::Op::DeleteByIdWithThis>(dst, *super_reference.base, *super_reference.this_value, identifier_table_ref);
             }
 
-            return Optional<ScopedOperand> {};
+            return dst;
         }
 
         auto object = TRY(expression.object().generate_bytecode(*this)).value();

Libraries/LibJS/Tests/operators/delete-basic.js

@@ -93,6 +93,13 @@ test("deleting super property", () => {
         }
     }
 
+    class D {
+        static foo() {
+            const deleter = () => delete super.foo;
+            deleter();
+        }
+    }
+
     const obj = new B();
     expect(() => {
         obj.bar();
@@ -106,6 +113,10 @@ test("deleting super property", () => {
     expect(() => {
         C.foo();
     }).toThrowWithMessage(ReferenceError, "Can't delete a property on 'super'");
+
+    expect(() => {
+        D.foo();
+    }).toThrowWithMessage(ReferenceError, "Can't delete a property on 'super'");
 });
 
 test("deleting an object computed property coerces the object to a property key", () => {