$.inArray doesn't crush IE6 and Chrome if second argument is null or undefined

Author: anton-ryzhov

src/core.js

@@ -678,6 +678,10 @@ jQuery.extend({
 	},
 
 	inArray: function( elem, array ) {
+		if (!jQuery.isArray(array))
+		{
+			return -1;
+		}
 
 		if ( indexOf ) {
 			return indexOf.call( array, elem );