Don't raise an error when json_decode() returns null and no error is …

…reported

Tests/format/JsonTest.php

@@ -143,4 +143,16 @@ public function testDataEqualityInConvertedObjects()
 
 		$this->assertEquals($input, $output, 'Input and output data must be equal.');
 	}
+
+	/**
+	 * @testdox  Validate an Exception is not thrown when a string is decoded to null and no error is reported
+	 *
+	 * @covers   Joomla\Registry\Format\Json::stringToObject
+	 */
+	public function testExceptionNotThrownWhenDecodedToNullWithoutError()
+	{
+		$class = new Json;
+
+		$this->assertInstanceOf('stdClass', $class->stringToObject('{}'));
+	}
 }

src/Format/Json.php

@@ -67,7 +67,7 @@ public function stringToObject($data, array $options = array('processSections' =
 		$decoded = json_decode($data);
 
 		// Check for an error decoding the data
-		if ($decoded === null)
+		if ($decoded === null && json_last_error() !== JSON_ERROR_NONE)
 		{
 			throw new \RuntimeException(sprintf('Error decoding JSON data: %s', json_last_error_msg()));
 		}