Call handleSave only if save was a success

[realVinayak]

Looks like usages assume that save was a success anyways

Fixes #5025

Checklist

• Self-review the PR after opening it to make sure the changes look good
  and self-explanatory (or properly documented)
• Add automated tests
• Add relevant issue to release milestone

Testing instructions

1. Open tree definition in the tree viewer
2. Try deleting a tree rank which has associated nodes (by clicking on -)
3. Verify that the error dialog appears, and the page doesn't automatically refresh
4. Make sure save buttons on forms, record sets, attachment gallery, app resource editor, resource dialogs work as expected