when sorting by last activity, if there was no activity use date

macosx/Controller.m

@@ -1632,10 +1632,10 @@ void sleepCallBack(void * controller, io_service_t y, natural_t messageType, voi
         descriptors = [[NSArray alloc] initWithObjects: orderDescriptor, nil];
     else if ([sortType isEqualToString: SORT_ACTIVITY])
     {
-        NSSortDescriptor * activityDescriptor = [[[NSSortDescriptor alloc] initWithKey: @"dateActivity" ascending: !asc] autorelease],
-                        * dateDescriptor = [[[NSSortDescriptor alloc] initWithKey: @"dateAdded" ascending: !asc] autorelease];
+        NSSortDescriptor * activityDescriptor = [[[NSSortDescriptor alloc] initWithKey: @"dateActivityOrAdd" ascending: !asc]
+                                                    autorelease];
         
-        descriptors = [[NSArray alloc] initWithObjects: activityDescriptor, dateDescriptor, orderDescriptor, nil];
+        descriptors = [[NSArray alloc] initWithObjects: activityDescriptor, orderDescriptor, nil];
     }
     else
     {

macosx/Torrent.h

@@ -223,6 +223,7 @@ typedef enum
 - (NSDate *) dateAdded;
 - (NSDate *) dateCompleted;
 - (NSDate *) dateActivity;
+- (NSDate *) dateActivityOrAdd;
 
 - (int) stalledMinutes;
 - (BOOL) isStalled;

macosx/Torrent.m

@@ -1332,6 +1332,12 @@ void completenessChangeCallback(tr_torrent * torrent, cp_status_t status, void *
     return date != 0 ? [NSDate dateWithTimeIntervalSince1970: date / 1000] : fDateActivity;
 }
 
+- (NSDate *) dateActivityOrAdd
+{
+    NSDate * date = [self dateActivity];
+    return date ? date : [self dateAdded];
+}
+
 - (int) stalledMinutes
 {
     uint64_t start;