Check that the filter is not undefined before encoding/decoding it.

If we include undefined filter values in the encoding/decoding,
then we store 'undefined' as the value in the cookie. When this
gets parsed out, it's treated as an actual value. This will likely
not match anything resulting in the initial filtering to filter out
all results.

dist/js/jquery.tablesorter.combined.js

@@ -1,4 +1,4 @@
-/*! tablesorter (FORK) - updated 01-15-2016 (v2.25.2)*/
+/*! tablesorter (FORK) - updated 01-19-2016 (v2.25.2)*/
 /* Includes widgets ( storage,uitheme,columns,filter,stickyHeaders,resizable,saveSort ) */
 (function(factory) {
 	if (typeof define === 'function' && define.amd) {
@@ -3701,7 +3701,9 @@
 				mode = encode ? encodeURIComponent : decodeURIComponent,
 				len = filters.length;
 			for ( indx = 0; indx < len; indx++ ) {
-				filters[ indx ] = mode( filters[ indx ] );
+				if ( typeof filters[ indx ] !== 'undefined' ) {
+					filters[ indx ] = mode( filters[ indx ] );
+				}
 			}
 			return filters;
 		},

dist/js/jquery.tablesorter.widgets.js

@@ -1,4 +1,4 @@
-/*! tablesorter (FORK) - updated 01-15-2016 (v2.25.2)*/
+/*! tablesorter (FORK) - updated 01-19-2016 (v2.25.2)*/
 /* Includes widgets ( storage,uitheme,columns,filter,stickyHeaders,resizable,saveSort ) */
 (function(factory) {
 	if (typeof define === 'function' && define.amd) {
@@ -983,7 +983,9 @@
 				mode = encode ? encodeURIComponent : decodeURIComponent,
 				len = filters.length;
 			for ( indx = 0; indx < len; indx++ ) {
-				filters[ indx ] = mode( filters[ indx ] );
+				if ( typeof filters[ indx ] !== 'undefined' ) {
+					filters[ indx ] = mode( filters[ indx ] );
+				}
 			}
 			return filters;
 		},

js/jquery.tablesorter.combined.js

@@ -4,7 +4,7 @@
 ██  ██ ██  ██   ██  ██ ██  ██   ██     ██ ██ ██ ██  ██ ██  ██ ██ ██▀▀    ▀▀▀██
 █████▀ ▀████▀   ██  ██ ▀████▀   ██     ██ ██ ██ ▀████▀ █████▀ ██ ██     █████▀
 */
-/*! tablesorter (FORK) - updated 01-15-2016 (v2.25.2)*/
+/*! tablesorter (FORK) - updated 01-19-2016 (v2.25.2)*/
 /* Includes widgets ( storage,uitheme,columns,filter,stickyHeaders,resizable,saveSort ) */
 (function(factory) {
 	if (typeof define === 'function' && define.amd) {
@@ -3707,7 +3707,9 @@
 				mode = encode ? encodeURIComponent : decodeURIComponent,
 				len = filters.length;
 			for ( indx = 0; indx < len; indx++ ) {
-				filters[ indx ] = mode( filters[ indx ] );
+				if ( typeof filters[ indx ] !== 'undefined' ) {
+					filters[ indx ] = mode( filters[ indx ] );
+				}
 			}
 			return filters;
 		},

js/jquery.tablesorter.widgets.js

@@ -4,7 +4,7 @@
 ██  ██ ██  ██   ██  ██ ██  ██   ██     ██ ██ ██ ██  ██ ██  ██ ██ ██▀▀    ▀▀▀██
 █████▀ ▀████▀   ██  ██ ▀████▀   ██     ██ ██ ██ ▀████▀ █████▀ ██ ██     █████▀
 */
-/*! tablesorter (FORK) - updated 01-15-2016 (v2.25.2)*/
+/*! tablesorter (FORK) - updated 01-19-2016 (v2.25.2)*/
 /* Includes widgets ( storage,uitheme,columns,filter,stickyHeaders,resizable,saveSort ) */
 (function(factory) {
 	if (typeof define === 'function' && define.amd) {
@@ -989,7 +989,9 @@
 				mode = encode ? encodeURIComponent : decodeURIComponent,
 				len = filters.length;
 			for ( indx = 0; indx < len; indx++ ) {
-				filters[ indx ] = mode( filters[ indx ] );
+				if ( typeof filters[ indx ] !== 'undefined' ) {
+					filters[ indx ] = mode( filters[ indx ] );
+				}
 			}
 			return filters;
 		},

js/widgets/widget-filter.js

@@ -615,7 +615,9 @@
 				mode = encode ? encodeURIComponent : decodeURIComponent,
 				len = filters.length;
 			for ( indx = 0; indx < len; indx++ ) {
-				filters[ indx ] = mode( filters[ indx ] );
+				if ( typeof filters[ indx ] !== 'undefined' ) {
+					filters[ indx ] = mode( filters[ indx ] );
+				}
 			}
 			return filters;
 		},

testing/testing-widgets.js

@@ -158,6 +158,18 @@ jQuery(function($){
 			assert.deepEqual( range( c, 'a-b-c,100' ), [ 0,1,2,3,4,5,6,7,8,9 ], 'text with dashes & commas -> all columns' );
 		});
 
+		QUnit.test( 'Filter process filters', function(assert) {
+			expect(2);
+			var processFilters = this.ts.filter.processFilters,
+				filters = [],
+				results = [];
+			filters[1] = 5, filters[2] = 'test', filters[3] = true;
+			results[1] = '5', results[2] = 'test', results[3] = 'true';
+
+			assert.deepEqual( processFilters( filters, true ),         results );
+			assert.deepEqual( processFilters( filters, false ),         results );
+		});
+
 		QUnit.test( 'Filter searches', function(assert) {
 			var ts = this.ts,
 				c = this.c,