Trampolines cease to work properly when put atop any carriable object

[Semphriss]

SuperTux version: 0.6.2 System information: Tested on Linux and Windows; it seems platform-independant.

Expected behavior

Trampolines lying on a building block, lantern, or any other carriable object, should allow Tux to bounce as if they were put normally on the ground.

Actual behavior

Trampolines on top of a carriable object will behave like an ordinary block. However, if you leave the trampoline by walking sideways (without jumping), you will bounce as normal.

Steps to reproduce actual behavior

Put a trampoline atop a building block or a lantern, then try to bounce on it. Optionnaly, try to leave the trampoline by walking sideways.

Video : https://youtu.be/sjCOIBL1Z5s

[Zwatotem]

I remember running across that bug when I was experimenting on rock-revamp branch. However, that was never merged, so probably I'm not on blame.

[mrkubax10]

This doesn't seem to be issue anymore

[mrkubax10]

Reopening as this still doesn't work when trampoline is placed on more than one object stack.