Fatal error: Call to a member function isMultiPlugin() on a non-object

Which PHP version?

Hi!
Sorry, I was quite busy today with client work.
The place to debug this is the class crumbs_PluginSystem_PluginMethodIterator.
As a typical iterator, this class has a current() method and a valid() method.
The current() method returns the value of the foreach(). If the valid() method returns FALSE, the loop stops.

Looking at the code, it seems as if the current() method should always return an object, if the valid() method previously returned TRUE.

Btw one of the docblock comments in PluginEngine is wrong, it should be

    /**
     * @var string $plugin_key
     * @var crumbs_PluginSystem_PluginMethodIteratorPosition $position
     */
    foreach ($iterator as $plugin_key => $position) {

So the $position is not a PluginMethodIterator, but a PluginMethodIteratorPosition.
But this docblock is not the cause of the error, obviously.

Of course we could make the valid() method more solid, like this:

  public function valid() {
    return isset($this->pluginKey) && isset($this->iteratorPosition);
  }

But it would be weird if $this->pluginKey is not NULL, while $this->iteratorPosition is NULL.

I just prepended if (!is_object($position)) continue;
The error appeared to me after i disabled the '*' plugin.

Fixed with http://cgit.drupalcode.org/crumbs/commit/?id=c1fcedb84f2a000e30dc62d0370...

This should really fix the issue, but it does not really explain what goes wrong in the iterator.
I thought for a moment that it is the confusion of FALSE vs NULL in crumbs_PluginSystem_PluginMethodIterator::setFirstValidIteratorPosition(). But this really can't be it. Whenever the pluginKey is something other than NULL, the iteratorPosition will be an object.