Enable nullable: System.Management.Automation.IContainsErrorRecord - #14166

 var icer = exception as IContainsErrorRecord;
if (icer == null)...

        /// <summary>
        /// Encode exception.
        /// </summary>
        private static PSObject EncodeException(Exception exception)
        {
            // We are encoding exceptions as ErrorRecord objects because exceptions written
            // to the wire are lost during serialization. By sending across ErrorRecord objects
            // we are able to preserve the exception as well as the stack trace.

            ErrorRecord errorRecord = null;
            IContainsErrorRecord containsErrorRecord = exception as IContainsErrorRecord;
            if (containsErrorRecord == null)
            {
                // If this is a .NET exception then wrap in an ErrorRecord.
                errorRecord = new ErrorRecord(exception, "RemoteHostExecutionException", ErrorCategory.NotSpecified, null);
            }
            else
            {
                // Exception inside the error record is ParentContainsErrorRecordException which
                // doesn't have stack trace. Replace it with top level exception.
                errorRecord = containsErrorRecord.ErrorRecord;
                errorRecord = new ErrorRecord(errorRecord, exception);
            }

            PSObject errorRecordPSObject = RemotingEncoder.CreateEmptyPSObject();
            errorRecord.ToPSObjectForRemoting(errorRecordPSObject);
            return errorRecordPSObject;
        }

        public ErrorRecord(ErrorRecord errorRecord,
                             Exception replaceParentContainsErrorRecordException)
        {
            if (errorRecord == null)
            {
                throw new PSArgumentNullException(nameof(errorRecord));
            }
}