Bug: If an audio track is the top track, mouse operation is not working.

Summary
Drag&drop a clip with the mouse from the bin should always overrule the green target indicator.

STEPS TO REPRODUCE

1. Create a project
2. Right click on V2 and add an audio track above V2
3. Delet track A3 on the bottom
4. Make A1 the only target track
5. Drag&drop a clip from the bin onto the timeline

OBSERVED RESULT

1. The clip can only be placed on A2 and V1 or on the target audio track A1.
2. Rendering doesn't work.

kdenlive-issue01

EXPECTED RESULT

1. Dragging the clip on A1 should place the video on V1.
2. Rendering should work

ADDITIONAL INFORMATION

Setting the target indicator as desired and working with shortcuts "v" the timeline works as expected.

A2_top_track_target_track_is_working