`HasError<T>` can throw, when I would expect `false`

[A9G-Data-Droid]

ISSUE:
When checking for the existence of a custom IError I sometimes get an exception that does not clearly point to the problem:

System.ArgumentNullException: Value cannot be null. (Parameter 'source')
at System.Linq.ThrowHelper.ThrowArgumentNullException(ExceptionArgument argument)
at System.Linq.Enumerable.OfType[TResult](IEnumerable source)
at FluentResults.ResultHelper.HasError[TError](List1 errors, Func2 predicate, IEnumerable1& result) at FluentResults.ResultHelper.HasError[TError](List1 errors, Func2 predicate, IEnumerable1& result)
at FluentResults.ResultBase.HasError[TError](Func2 predicate, IEnumerable1& result)
at FluentResults.ResultBase.HasError[TError](IEnumerable`1& result)
at FluentResults.ResultBase.HasErrorTError

EXPECTED BEHAVIOR:
I would expect HasError<T> to return false instead of throwing.

CAUSE:
In my custom error I did not initialize Reasons in some cases.

SOLUTION:
I would recommend turning on <nullable>enable</nullable> to help flag null problems across the code base.

The problem seems to be in [public static bool HasError(](

FluentResults/src/FluentResults/Factories/ResultHelper.cs

Line 35 in 8b675de

var foundErrors = errors.OfType<TError>().Where(predicate).ToList();

)

where predicate is null when looking at a null set of Reasons.

Adding

if(predicate is null) return false

is an example fix.

[altmann]

Implemented with v3.16