design does not autofit on new design load

[sarahayu]

This is the second bug mentioned in issue #768, but since I've found its cause elusive and I think different from the first rope select bug, plus the reproduction steps there are convoluted, I've made a separate issue. Steps to reproduce:

1. Load example 2_staple_2_helix_origami_deletions_insertions_mods
2. Click a part of the design that isn't the background i.e. any part where you would click+drag, and it will NOT move the design (ex: helix grid, strands/domains, helix numbers)
3. Load example 6_helix_origami_rectangle
4. Design is not autofitted. Clicking the "autofit" option in the menu will still not autofit it, unless you click any part of the background and then click "autofit" afterwards.