Ensures call stack location object exists before calling methods on it
Ensures call stack location object exists before calling methods on it

Fixes the error:
TypeError: Cannot call method 'getFunctionName' of undefined

In longjohn.js:call_stack_location(), if the object stack[2] is not defined it crashes the server with an uncaught exception.

Signed-off-by: Jim Knochelmann <1cd02e31b43620d7c664e038ca42a060d61727b9@airspringsoftware.com>

mattinsler/longjohn