Black screen when parenting a null object

[AgentOriginality]

Hi, Im currently making an edit and Im trying to make a transition, however when I start parenting a null object, the footage goes completely black. What should I do?

[Rick Gerard · Accepted solution]

You did not parent a null; you tried to use a layer with no pixels, the null, as an Alpha track Matte. Pay close attention to the column headings.

Turn off the track matte, press Shift + F4 to reveal the Parent/Link column, and set the Null as the parent for the bottom layer.