Core: Return empty array instead of null for parseHTML("")

Fixes gh-1997
Close gh-1998

Conflicts:
	test/unit/core.js

src/core/parseHTML.js

@@ -14,8 +14,8 @@ define([
 // defaults to document
 // keepScripts (optional): If true, will include scripts passed in the html string
 jQuery.parseHTML = function( data, context, keepScripts ) {
-	if ( !data || typeof data !== "string" ) {
-		return null;
+	if ( typeof data !== "string" ) {
+		return [];
 	}
 	if ( typeof context === "boolean" ) {
 		keepScripts = context;

test/unit/core.js

@@ -1285,13 +1285,18 @@ test("jQuery.proxy", function(){
 });
 
 test("jQuery.parseHTML", function() {
-	expect( 17 );
+	expect( 22 );
 
 	var html, nodes;
 
-	equal( jQuery.parseHTML(), null, "Nothing in, null out." );
-	equal( jQuery.parseHTML( null ), null, "Null in, null out." );
-	equal( jQuery.parseHTML( "" ), null, "Empty string in, null out." );
+	deepEqual( jQuery.parseHTML(), [], "Without arguments" );
+	deepEqual( jQuery.parseHTML( undefined ), [], "Undefined" );
+	deepEqual( jQuery.parseHTML( null ), [], "Null" );
+	deepEqual( jQuery.parseHTML( false ), [], "Boolean false" );
+	deepEqual( jQuery.parseHTML( 0 ), [], "Zero" );
+	deepEqual( jQuery.parseHTML( true ), [], "Boolean true" );
+	deepEqual( jQuery.parseHTML( 42 ), [], "Positive number" );
+	deepEqual( jQuery.parseHTML( "" ), [], "Empty string" );
 	throws(function() {
 		jQuery.parseHTML( "<div></div>", document.getElementById("form") );
 	}, "Passing an element as the context raises an exception (context should be a document)");