Merge pull request #51 from chamilo/1.9.x

1.9.x
Merge pull request #53 from chamilo/1.9.x

1.9.x
Verifiying if user can be subscribed -refs #6648
Verifiying if user can be subscribed -refs #6662
Merge pull request #279 from ycastillo/fix.6662

Fix.6662