Added DateHeaderCell to prevent drunk sorting on null dates

UI/Series/Index/SeriesIndexLayout.js

@@ -10,6 +10,7 @@ define(
         'Cells/SeriesTitleCell',
         'Cells/TemplatedCell',
         'Cells/QualityProfileCell',
+        'Shared/Grid/DateHeaderCell',
         'Series/Index/Table/SeriesStatusCell',
         'Series/Index/Table/Row',
         'Series/Index/FooterView',
@@ -25,6 +26,7 @@ define(
                  SeriesTitleCell,
                  TemplatedCell,
                  QualityProfileCell,
+                 DateHeaderCell,
                  SeriesStatusCell,
                  SeriesIndexRow,
                  FooterView,
@@ -71,7 +73,8 @@ define(
                     {
                         name      : 'nextAiring',
                         label     : 'Next Airing',
-                        cell : RelativeDateCell
+                        cell      : RelativeDateCell,
+                        headerCell: DateHeaderCell
                     },
                     {
                         name    : 'this',

UI/Shared/Grid/DateHeaderCell.js

@@ -0,0 +1,66 @@
+'use strict';
+
+define(
+    [
+        'backgrid',
+        'Shared/Grid/HeaderCell'
+    ], function (Backgrid, NzbDroneHeaderCell) {
+
+        Backgrid.DateHeaderCell = NzbDroneHeaderCell.extend({
+            events: {
+                'click': 'onClick'
+            },
+
+            onClick: function (e) {
+                e.preventDefault();
+
+                var self = this;
+                var columnName = this.column.get('name');
+
+                if (this.column.get('sortable')) {
+                    if (this.direction() === 'ascending') {
+                        this.sort(columnName, 'descending', function (left, right) {
+                            var leftVal = left.get(columnName);
+                            var rightVal = right.get(columnName);
+
+                            return self._comparator(leftVal, rightVal)
+                        });
+                    }
+                    else {
+                        this.sort(columnName, 'ascending', function (left, right) {
+                            var leftVal = left.get(columnName);
+                            var rightVal = right.get(columnName);
+
+                            return self._comparator(rightVal, leftVal)
+                        });
+                    }
+                }
+            },
+
+            _comparator: function (leftVal, rightVal) {
+                if (!leftVal && !rightVal) {
+                    return 0
+                }
+
+                if (!leftVal) {
+                    return -1;
+                }
+
+                if (!rightVal) {
+                    return 1
+                }
+
+                if (leftVal === rightVal) {
+                    return 0;
+                }
+
+                if (leftVal > rightVal) {
+                    return -1;
+                }
+
+                return 1;
+            }
+        });
+
+        return Backgrid.DateHeaderCell;
+    });