Running cronjobs/workflow.php
   Checking for workflow processes

   Fatal error: Call to a member function attribute() on a non-object in /data/orig/securitycenter/sc401/kernel/content/ezcontentoperationcollection.php on line 306

   Fatal error: eZ Publish did not finish its request
   The execution of eZ Publish was abruptly ended, the debug output is present below.

Basic Steps:
1. Install fresh eZ Publish 4.0.1
2. Create a new user(test) under Editor  
3. Give proper access to Editor user group so users of this group can login to site admin interface.
4. Go to Setup -> Workflows -> Standard
5. Create new work flow let say "Test workflow"
    Add new Approve Event with following specification.
         Affected sections: All sections
         Affected languages: All language 
         Affected versions: All versions
        Users who approve content :: (Select the <test>user from Editor user group)
   Click on "OK" button

6. Go to Setup -> Triggers (Select "Test workflow") for 
    content 	publish 	before
7. Click on Apply Changes.




Reproducable steps.
a) Login to admin interface with admin user.
b) Create a object of any class let's say folder class and let's name it "AABBCC".
c) Login to admin interface with "test" user.
d) Go to "My account" -> "Collaboration"
e) Approve the object from item list.
f) run the cronjob from command line "php ./runcronjobs.php frequent".
g) Again login to admin interface with "admin" user and go to "Content Structure" -> "AABBCC"
h) Create another object below this node let's name it  "EEFFGG".
i) Again follow above  steps from (c) to (g)
j) Edit node "EEFFGG" and republish the object.
k) Now move "EEFFGG" node to root node(2)
l) Approve node "EEFFGG" 
m) now again run the cronjob from command line "php ./runcronjobs.php frequent".
   and you will get following error
   Running cronjobs/workflow.php
   Checking for workflow processes

   Fatal error: Call to a member function attribute() on a non-object in /data/orig/securitycenter/sc401/kernel/content/ezcontentoperationcollection.php on line 306

   Fatal error: eZ Publish did not finish its request
   The execution of eZ Publish was abruptly ended, the debug output is present below.
J) Check Colloboration list for "test" user it is empty.
k) Now if again we execute "php ./runcronjobs.php frequent".
    Check the Colloboration list for "test" user and that item again re appears for approval.
l) This Collaboration items never gets approved every second time we run "php ./runcronjobs.php frequent". that colloboration re appears.