VIX-3791 Fix exception in Vixen export type

* Ensure the correct type is presented to the serializer.
* Add exception handling logic to prevent crashes if the serialization fails

Author: jeffu231

src/Vixen.Modules/Editor/TimedSequenceEditor/Forms/WPF/MarksDocker/Services/MarkImportExportService.cs

@@ -547,10 +547,18 @@ public static async Task ExportMarkCollections(MarkExportType exportType, IList<
 						IndentChars = "\t"
 					};
 
-					DataContractSerializer ser = CreateSerializer(typeof(List<IMarkCollection>), false);
-					var writer = XmlWriter.Create(saveFileDialog.FileName, xmlsettings);
-					ser.WriteObject(writer, collections.Select(x => x.MarkCollection));
-					writer.Close();
+					try
+					{
+						DataContractSerializer ser = CreateSerializer(typeof(List<IMarkCollection>), false);
+						var writer = XmlWriter.Create(saveFileDialog.FileName, xmlsettings);
+						ser.WriteObject(writer, collections.Select(x => x.MarkCollection).ToList());
+						writer.Close();
+					}
+					catch (Exception ex)
+					{
+						Logging.Error(ex,"An exception occured trying to export the mark collection");
+					}
+					
 				}
 			}