Handling TypeScript Error for Possibly Null `existingUser` in Effect Code

const existingUser = yield* Effect.tryPromise({
  try: () => get_user_by_email(client, {
             email: form.data.email,
    }),
  catch: () => new ServerError({ errors: ["User not found"] }) });

if (!existingUser || !existingUser?.password || !existingUser.email) {
  yield* Effect.fail(
    new CustomInputError({ 
      form,
      field: ["email", "password"],
      message: "Incorrect Email or Password", }),
    );
  }

const isPasswordValid = yield* Effect.tryPromise({
  try: () =>   bcryptjs.compare(form.data.password, existingUser.password),
  catch: () => new ServerError({ errors:  
["Invalid password"] }) 
});

const existingUser = yield* Effect.tryPromise({
  try: () => get_user_by_email(client, {
             email: form.data.email,
    }),
  catch: () => new ServerError({ errors: ["User not found"] }) });

if (!existingUser || !existingUser?.password || !existingUser.email) {
  yield* Effect.fail(
    new CustomInputError({ 
      form,
      field: ["email", "password"],
      message: "Incorrect Email or Password", }),
    );
  }

const isPasswordValid = yield* Effect.tryPromise({
  try: () =>   bcryptjs.compare(form.data.password, existingUser.password),
  catch: () => new ServerError({ errors:  
["Invalid password"] }) 
});

bcryptjs.compare(form.data.password, existingUser.password)

bcryptjs.compare(form.data.password, existingUser.password)