Added unittest that shows the trickers the bug.
Test added in test_delete_spin_all, and can be accessed with: relax -u _pipe_control.test_spin.
Bug #23642 (https://gna.org/bugs/index.php?23642): When deleting all spins for a residue, an empty placeholder is where select=True
Authored by: tlinnet 2015-06-13
Parent: [r27848]
Child: [r27850]
