Web Client: Check In Should Not Fail Silently

Evergreen 3.0.x

When a checkin fails in the XUL client, an error message is displayed. This lets library staff know the checkin failed and gives a general idea of why.

When a checkin fails in the web client, it appears to the library staff that nothing happens. After scanning in the barcode, the barcode disappears from the submit box, and then... nothing. This makes it difficult to tell what happened and can easily lead to staff not realizing an item did not check in.

If looking at Chrome's console, the error will display. For example, we have a small subset of items in the status Lost that are not attached to a patron's account, (these were migrated from our old system years ago). We know these items give an error if checked in. The console outputs the following error:
net.js:119 error calling method open-ils.circ.checkin : 500 : *** Call to [open-ils.circ.checkin] failed for session [0.055672899036750321534190680104], thread trace [0]:
Can't call method "id" on an undefined value at /usr/local/share/perl/5.14.2/OpenILS/Application/Circ/Circulate.pm line 2371.

Our staff do not know to look at the console, and they shouldn't need to just to be told a checkin failed. Evergreen should display some form of visual acknowledgement that the checkin failed. I do not think this has to be the error message that displayed in the XUL, as even a simple message that says "Check In Failed" would be more useful than failing silently.