menu option given for morph to be attached to non-overlapping clipped morphs

[davidedc]

steps:

• open a scrollframe
• drop in the scrollframe an animation demo
• create a rectangle and position it just under the scrollmorph like so:
• right-click on the rectangle and choose attach to...

obtained:

• options are given to select the frame morph and the bounce morphs, none of which overlaps with the rectangle like so:

expected:

• no morphs are eligible for attachment

(this was fixed in Zombie Kernel but I can't remember when, would need bisection)