Check that args are present before mapping over

Closes #2925

src/buffered-process.coffee

@@ -45,7 +45,10 @@ class BufferedProcess
     # Related to joyent/node#2318
     if process.platform is "win32"
       # Quote all arguments and escapes inner quotes
-      cmdArgs = args.map (arg) -> "\"#{arg.replace(/"/g, '\\"')}\""
+      if args?
+        cmdArgs = args.map (arg) -> "\"#{arg.replace(/"/g, '\\"')}\""
+      else
+        cmdArgs = []
       cmdArgs.unshift("\"#{command}\"")
       cmdArgs = ['/s', '/c', "\"#{cmdArgs.join(' ')}\""]
       cmdOptions = _.clone(options)