Fix a problem of tag values which is not taken into account

(when equal to zero) when passing an XML object to an array.

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

@@ -644,6 +644,16 @@ XML;
 			)
 		);
 		$this->assertEquals($expected, Xml::toArray($obj));
+
+		$xml = '<tag type="myType">0</tag>';
+		$obj = Xml::build($xml);
+		$expected = array(
+			'tag' => array(
+				'@type' => 'myType',
+				'@' => 0
+			)
+		);
+		$this->assertEquals($expected, Xml::toArray($obj));
 	}
 
 /**

lib/Cake/Utility/Xml.php

@@ -360,7 +360,7 @@ class Xml {
 		$asString = trim((string)$xml);
 		if (empty($data)) {
 			$data = $asString;
-		} elseif (!empty($asString)) {
+		} elseif (strlen($asString) > 0) {
 			$data['@'] = $asString;
 		}