jquery fx: closes #2542. show/hide(0, fn) wasn't calling the callback.

src/fx.js

@@ -19,7 +19,7 @@ function genFx( type, num ){
 
 jQuery.fn.extend({
 	show: function(speed,callback){
-		if ( speed ) {
+		if ( speed !== undefined ) {
 			return this.animate( genFx("show", 3), speed, callback);
 		} else {
 			for ( var i = 0, l = this.length; i < l; i++ ){
@@ -59,7 +59,7 @@ jQuery.fn.extend({
 	},
 
 	hide: function(speed,callback){
-		if ( speed ) {
+		if ( speed !== undefined ) {
 			return this.animate( genFx("hide", 3), speed, callback);
 		} else {
 			for ( var i = 0, l = this.length; i < l; i++ ){

test/unit/fx.js

@@ -68,7 +68,7 @@ test("animate option (queue === false)", function () {
 */
 
 test("animate duration 0", function() {
-	expect(5);
+	expect(7);
 	
 	stop();
 	
@@ -97,7 +97,15 @@ test("animate duration 0", function() {
 		// Failed until [6115]
 		equals( counter, 5, "One synchronic and one asynchronic" );
 		start();
-	});	
+	});
+	
+	var $elem = jQuery("<div />");
+	$elem.show(0, function(){ 
+		ok(true, "Show's callback with no duration");
+	});
+	$elem.hide(0, function(){ 
+		ok(true, "Show's callback with no duration");
+	});
 });
 
 test("animate hyphenated properties", function(){