You should be able to regex match null/''

Fixes #2926

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

@@ -846,6 +846,29 @@ class HashTest extends CakeTestCase {
 		$this->assertEquals($expected, $result);
 	}
 
+/**
+ * Test that extract() + matching can hit null things.
+ */
+	public function testExtractMatchesNull() {
+		$data = array(
+			'Country' => array(
+				array('name' => 'Canada'),
+				array('name' => 'Australia'),
+				array('name' => null),
+			)
+		);
+		$result = Hash::extract($data, 'Country.{n}[name=/Canada|^$/]');
+		$expected = array(
+			array(
+				'name' => 'Canada',
+			),
+			array(
+				'name' => null,
+			),
+		);
+		$this->assertEquals($expected, $result);
+	}
+
 /**
  * Test that uneven keys are handled correctly.
  *

lib/Cake/Utility/Hash.php

@@ -192,7 +192,7 @@ class Hash {
 			}
 
 			// Empty attribute = fail.
-			if (!isset($data[$attr])) {
+			if (!(isset($data[$attr]) || array_key_exists($attr, $data))) {
 				return false;
 			}