Fix #77 - Added explanation about exception to rule G-5040 in case of proper use of Logger.

Author: kibeha

docs/4-language-usage/5-exception-handling/g-5040.md

@@ -7,6 +7,8 @@
 
 There is not necessarily anything wrong with using `when others`, but it can cause you to "lose" error information unless your handler code is relatively sophisticated. Generally, you should use `when others` to grab any and every error only after you have thought about your executable section and decided that you are not able to trap any specific exceptions. If you know, on the other hand, that a certain exception might be raised, include a handler for that error. By declaring two different exception handlers, the code more clearly states what we expect to have happen and how we want to handle the errors. That makes it easier to maintain and enhance. We also avoid hard-coding error numbers in checks against `sqlcode`.
 
+When using a logging framework like Logger, consider making an exception to this rule and allow a `when others` even without other specific handlers, but *only* if the `when others` exception handler calls a logging procedure that saves the error stack (that otherwise is lost) and the last statement of the handler is `raise`.
+
 ## Example (bad)
 
 ``` sql
@@ -29,4 +31,17 @@ exception
       my_package.some_further_processing();
 end;
 /
+```
+
+## Example (exception to the rule)
+
+``` sql
+begin
+   my_package.some_processing();
+exception
+   when others then
+      logger.log_error('Unhandled Exception');
+      raise;
+end;
+/
 ```