Make sure invalid arrays return empty array instead of throwing notices.

lib/Cake/Test/Case/Utility/HashTest.php

@@ -2242,6 +2242,25 @@ class HashTest extends CakeTestCase {
 		$this->assertEquals($input, $result);
 	}
 
+/**
+ * Tests that nest() returns an empty array for invalid input instead of throwing notices.
+ *
+ * @return void
+ */
+	public function testNestInvalid() {
+		$input = array(
+			array(
+				'ParentCategory' => array(
+					'id' => '1',
+					'name' => 'Lorem ipsum dolor sit amet',
+					'parent_id' => '1'
+				)
+			)
+		);
+		$result = Hash::nest($input);
+		$this->assertSame(array(), $result);
+	}
+
 /**
  * testMergeDiff method
  *

lib/Cake/Utility/Hash.php

@@ -1037,6 +1037,8 @@ class Hash {
 
 		if ($options['root']) {
 			$root = $options['root'];
+		} elseif (!$return) {
+			return array();
 		} else {
 			$root = self::get($return[0], $parentKeys);
 		}