isNaN() doesn't check if the value is numeric; it only checks if it i…

…s equal to NaN. In particular it won't catch null.

lib/forever.js

@@ -972,7 +972,7 @@ forever.logEvents = function (monitor) {
   });
 
   monitor.on('exit:code', function (code, signal) {
-    forever.out.error(!isNaN(code)
+    forever.out.error((code !== null && code !== undefined)
       ? 'Forever detected script exited with code: ' + code
       : 'Forever detected script was killed by signal: ' + signal);
   });