chore(logging): fix logging.error and make sure logger exists

src/logging.js

@@ -18,17 +18,21 @@ if (logger == null) {
 // A custom log function that wraps Winston. Makes it easy to instrument code
 // and still possible to replace Winston in the future.
 module.exports.log = function(/* variable args */) {
-    logger.log.apply(logger, arguments);
+    if (logger)
+        logger.log.apply(logger, arguments);
 };
 
 module.exports.info = function(/* variable args */) {
-   logger.info.apply(logger, arguments);
+    if (logger)
+        logger.info.apply(logger, arguments);
 };
 
 module.exports.warn = function(/* variable args */) {
-    logger.warn.apply(logger, arguments);
+    if (logger)
+        logger.warn.apply(logger, arguments);
 };
 
 module.exports.error = function(/* variable args */) {
-    winston.error(arguments);
+    if (logger)
+        logger.error.apply(logger, arguments);
 };