When we use an SQLite.Ignore decorated property inside an expression.

Minor change. More descriptive error (it thows now 'Null reference exception') ... When we use an SQLite.Ignore decorated property inside an expression.

To Test: 
Just decorate a property in your class with [SQLite.Ignore] and try to use that property inside an expresion like:
db.Table<Example>().OrderBy(ex=>ex.SQLiteIgnoredProperty)