Make sure that empty nodelists continue to map properly. Fixes #8993.

src/core.js

@@ -720,7 +720,7 @@ jQuery.extend({
 			i = 0,
 			length = elems.length,
 			// jquery objects are treated as arrays
-			isArray = elems instanceof jQuery || length !== undefined && typeof length === "number" && ( ( length > 0 && elems[ 0 ] && elems[ length -1 ] ) || jQuery.isArray( elems ) ) ;
+			isArray = elems instanceof jQuery || length !== undefined && typeof length === "number" && ( ( length > 0 && elems[ 0 ] && elems[ length -1 ] ) || length === 0 || jQuery.isArray( elems ) ) ;
 
 		// Go through the array, translating each of the items to their
 		if ( isArray ) {

test/unit/core.js

@@ -653,7 +653,7 @@ test("first()/last()", function() {
 });
 
 test("map()", function() {
-	expect(7);
+	expect(8);
 
 	same(
 		jQuery("#ap").map(function(){
@@ -694,6 +694,12 @@ test("map()", function() {
 	});
 	equals( mapped.length, scripts.length, "Map an array(-like) to a hash" );
 
+	var nonsense = document.getElementsByTagName("asdf");
+	var mapped = jQuery.map( nonsense, function( v, k ){
+		return v;
+	});
+	equals( mapped.length, nonsense.length, "Map an empty array(-like) to a hash" );
+
 	var flat = jQuery.map( Array(4), function( v, k ){
 		return k % 2 ? k : [k,k,k];//try mixing array and regular returns
 	});