517732 - Don't abuse try-catch to work around proper error checking

Status: NEW

(SeaMonkey :: MailNews: General, defect)

Description

[Karsten Düsterloh]

We've quite some function in mailnews land which, instead of proper error checking, just wrap up stuff in a try-catch block. 
We should use try-catch only for catching exceptions, not errors.
(On a sidenote, these error catches unnecessarily clutter Venkman's Interactive Session window.)

Example: gDBView problems are frequently handled that way, e.g. 
| Error ``gDBView is null'' [x-] in file 
| ``chrome://messenger/content/mail3PaneWindowCommands.js'', 
| line 760, character 0.

function GetNumSelectedMessages()
{
    try {
        return gDBView.numSelected;
    }
    catch (ex) {
        return 0;
    }
}

should just be

function GetNumSelectedMessages()
{
  if (gDBView)
    return gDBView.numSelected;
  return 0;
}

(given that numSelected doesn't throw exceptions which I didn't check).