Could i use the on first window open script to set field ( container ) to a large image, trap for errors, and let the error code tell me that there is not enough free space to run the app? what code should i trap for or will any error code be sufficient?
Try it and see.
I wouldn't have any idea what error code might be thrown in such a situation, since it's an iOS-level issue, not a FileMaker one. You may not get a FileMaker error code at all, or you may get an 800 (could not create file on disk), 809 (disk is full), 810 (disk is locked), or any of a number of other errors. My first guess would be something in the 800 series, but you won't know until you try it.
I had the same problem with an old iPad and 16 GB, my restaurant FM application. Sometimes, the application crashes when typing data, no error and no reason.
I replace with a new one with 64 GB and now no more crash.
Interestingly enough, I have a client using an app on both older iPads and newer ones. They say it crashes when they rotate the device to take a photo, then rotate it back. I can't get it to crash on my iPad, nor can one of the company owners on hers. The only common thread is the storage space is smaller on the iPads where the crashing behavior is showing up (but only sporadically).
As I said, interesting ...
Tried and failed to capture the error.
The "phone is full" condition is caught before the FM file is opened.
Know any of the FMI FM GO Engineers?
I suspect it's an iOS thing, then. There may not be anything you can do.