When clicking on an already-selected keyframe, mark it as active if the click caused the previously-active keyframe to become deselected. When clicking on a key in the graph editor, it is selected and all other keys are deselected. If that key was already selected before the click, it would not become the active keyframe. This is now fixed. Reviewed by: Severin Differential Revision: https://developer.blender.org/D9639