The plugin context system now considers FALSE to be a valid value

Previously the context system would return FALSE for the hasContextValue method on a context object if the value was set to FALSE, even though this is a perfectly valid value.

Now, hasContextValue will return TRUE, only a value of NULL will cause hasContextValue to return FALSE

Before

$definition = new \Drupal\Core\Plugin\Context\ContextDefinition('boolean');
$context = new \Drupal\Component\Plugin\Context\Context($definition, FALSE);
$context->hasContextValue(); // Would return FALSE

After

$definition = new \Drupal\Core\Plugin\Context\ContextDefinition('boolean');
$context = new \Drupal\Component\Plugin\Context\Context($definition, FALSE);
$context->hasContextValue(); // Now returns TRUE