Fixed: Sort by Next Airing will always keep empty values at the bottom

src/UI/Mixins/AsSortedCollection.js

@@ -81,8 +81,8 @@ define(
                 }
 
                 return function (left, right) {
-                    var l = sortValue(left, sortKey);
-                    var r = sortValue(right, sortKey);
+                    var l = sortValue(left, sortKey, order);
+                    var r = sortValue(right, sortKey, order);
                     var t;
 
                     if (order === 1) {
@@ -94,8 +94,8 @@ define(
                     if (l === r) {
 
                         if (secondarySorting) {
-                            var ls = secondarySorting.sortValue(left, secondarySorting.key);
-                            var rs = secondarySorting.sortValue(right, secondarySorting.key);
+                            var ls = secondarySorting.sortValue(left, secondarySorting.key, order);
+                            var rs = secondarySorting.sortValue(right, secondarySorting.key, order);
                             var ts;
 
                             if (secondarySorting.order === 1) {

src/UI/Series/SeriesCollection.js

@@ -62,21 +62,19 @@ define(
             sortMappings: {
                 'title'      : { sortKey: 'sortTitle' },
                 'nextAiring' : {
-                    sortValue: function (model, attr) {
-                                    var nextAiring = model.get(attr);
-                                    
-                                    if (nextAiring) {
-                                        return moment(nextAiring).unix();
-                                    }
-                                    
-                                    var previousAiring = model.get(attr.replace('nextAiring', 'previousAiring'));
-                                    
-                                    if (previousAiring) {
-                                        return 10000000000 - moment(previousAiring).unix();
-                                    }
-
-                                    return Number.MAX_VALUE;
-                                }
+                    sortValue: function (model, attr, order) {
+                        var nextAiring = model.get(attr);
+
+                        if (nextAiring) {
+                            return moment(nextAiring).unix();
+                        }
+
+                        if (order === 1) {
+                            return 0;
+                        }
+
+                        return Number.MAX_VALUE;
+                    }
                 },
 
                 percentOfEpisodes: {