Add Error backtrace if within the Application Frame

I have an application controller with a `rescue_from` clause that catches a custom error.

However the Application Frames tab is only showing one single line, the current one, and I must manually explore the backtrace_locations within the live shell.

I understand that with `rescue_from` the exception object might not be available, so the implementation might be tricky.

I would be happy even with a dirty hack enabling me to manually add the line to the Application Frames of the error page, but maybe that is another type of feature request?