gracefully handle incorrect form input. fixes #1425 and refs #1413

controllers should not throw exceptions when handling form input.

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #1425
| Refs tickets  | #1413
| License       | MIT
| Doc PR        | -