Field access should propagate the exception (Err(_))

[HalidOdat]

When ToObject (to_object) throws an error the field accessors don't propagate the error in GetConstField and GetField nodes

GetConstField: https://github.com/boa-dev/boa/blob/master/boa/src/exec/field/mod.rs#L12-L13
GetField: https://github.com/boa-dev/boa/blob/master/boa/src/exec/field/mod.rs#L25-L26

To fix this we should change from .expect("failed to convert to object") to ? try operator.

[neeldug]

Hi,

Would like to work on this issue.

Thanks