LibJS: Fix not executing the expression of a return statement

Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp

@@ -401,6 +401,8 @@ void CallExpression::generate_bytecode(Bytecode::Generator& generator) const
 
 void ReturnStatement::generate_bytecode(Bytecode::Generator& generator) const
 {
+    if (m_argument)
+        m_argument->generate_bytecode(generator);
     generator.emit<Bytecode::Op::Return>();
 }