FSO Crashes when trying to read a "malformed" pilot file

Instead, it should kick up a warning dialog and allow the player to proceed.

This issue pops up when trying to use an older version of FSO with the new pilot files within the Controls PR's #2958 . ~~A stopgap which may or may not work is to enforce writing a blank section instead of removal in order to prevent the crash.~~ Writing a blank section won't work, the new pilot files in #2958 retain the controls section but use it to define a preset instead of all of the controls.

It looks like the codebase uses an Error dialog, but this error doesn't allow you to get past it as a user.