Description:
------------
If isDefaultValueAvailable() returns TRUE I expect to be able to call 
getDefaultValue()

Test script:
---------------
<?php
class a {
	protected function test(array $a = NULL, $b, array $c = NULL) {}
}

$class = new ReflectionClass('a');
foreach ($class->getMethods() as $method) {
	foreach ($method->getParameters() as $p) {
	    echo $p->getName() . "\n";
	    echo "   isDefaultValueAvailable: " . var_export($p->isDefaultValueAvailable(), true) . "\n";
		if ($p->isDefaultValueAvailable()) {
			echo "    default value: " . var_export($p->getDefaultValue(), true) . "\n";
		}
	    echo "    isOptional: " . var_export($p->isOptional(), true) . "\n";
	    echo "    allowsNull: " . var_export($p->allowsNull(), true) . "\n";
	    echo "\n";
	}
}
?>

Expected result:
----------------
a
   isDefaultValueAvailable: true
    default value: NULL
    isOptional: false
    allowsNull: true

b
   isDefaultValueAvailable: false
    isOptional: false
    allowsNull: true

c
   isDefaultValueAvailable: true
    default value: NULL
    isOptional: true
    allowsNull: true

Actual result:
--------------
a
   isDefaultValueAvailable: true

Fatal error: Uncaught exception 'ReflectionException' with message 'Parameter is 
not optional' in test.php on line 12

ReflectionException: Parameter is not optional in test.php on line 12

Call Stack:
    0.0010     646632   1. {main}() test.php:0
    0.0011     651128   2. ReflectionParameter->getDefaultValue() test.php:12