Blender Git Loki

Animation: Change active FCurve in box/circle/lasso select

Update the active FCurve when box/circle/lasso-selecting, such that after
the operator has finished the active curve is actually the last-operated-on
FCurve.

The operator already would deactivate the active FCurve. However, it would
not re-activate one any more, which caused the active keyframe to become
inactive.