Better Message for Invalid + Operation

I tried to use EL to access the `Optional` in a record.

```java
public record PhoneNumber(String countryCode, String number) {
}
```

And the `Customer`:

```java
public record Customer(
String firstName,
String lastName,
Optional phoneNumber,
EmailAddress[] emailAddresses,
Address address
) {
}
```

And evaluate the following expression.

```
String phoneNumber = elProcessor.eval("customer.phoneNumber.map(t-> t.countryCode+t.number).orElse('NotFound')");
System.out.println(phoneNumber);

```

It throws an exception,

```bash
java.lang.ClassCastException: class java.lang.Long cannot be cast to
class java.lang.String (java.lang.Long and java.lang.String are in
module java.base of loader 'bootstrap')
```
**But there is no `Long` type field in EL expression**.

As suggested by @OndroMih, it is better to show a message to indicate what is wrong, which will help developers to locate the issues quickly.

```bash
customer.phoneNumber.map(t-> t.countryCode[>>> + ]t.number).orElse('NotFound')
```

BTW: Replace the `map()` function with `map(t -> t.contryCode.concat(t.number))`, and it works.