MH-9859 no more needless calls for space.png in chrome

git-svn-id: https://opencast.jira.com/svn/MH/trunk@15642 e6edf6fb-f266-4316-afb4-e53d95876a76
MH-9869, added namespace to elements searched for
Issue #MH-9869 - Engage (embedded) doesn't show video preview image

git-svn-id: https://opencast.jira.com/svn/MH/trunk@15643 e6edf6fb-f266-4316-afb4-e53d95876a76