'Network error' message is reported in expression evaluation using deferred library

[annagrin]

If the library used by the expression is not loaded yet, DDC produces JavaScript that will trigger loading the module (and XHR call) when evaluated in chrome. If the expression evaluation is performed on pause, XHR call completes with a network error.

We don't know yet how common such evaluations are, so for now we should just report a better error and collect analytics.