Add cleaner cleaning tests

SabreTools.Filtering/Cleaner.cs

@@ -123,7 +123,7 @@ namespace SabreTools.Filtering
         /// <summary>
         /// Logging object
         /// </summary>
-        private Logger logger = new Logger();
+        private readonly Logger logger = new Logger();
 
         #endregion
 
@@ -140,6 +140,10 @@ namespace SabreTools.Filtering
             ExcludeMachineFields ??= new List<MachineField>();
             ExcludeDatItemFields ??= new List<DatItemField>();
 
+            // If the list is null or empty, just return
+            if (fields == null || fields.Count == 0)
+                return;
+
             foreach (string field in fields)
             {                
                 // If we don't even have a possible field name
@@ -186,6 +190,10 @@ namespace SabreTools.Filtering
             MachineFilter ??= new MachineFilter();
             DatItemFilter ??= new DatItemFilter();
 
+            // If the list is null or empty, just return
+            if (filters == null || filters.Count == 0)
+                return;
+
             foreach (string filterPair in filters)
             {
                 (string field, string value, bool negate) = ProcessFilterPair(filterPair);