Fixed NullPointerException with i18n.

i18n class may not be initialized during init time.

Author: cmaglie

app/src/processing/app/I18n.java

@@ -53,7 +53,10 @@ static protected void init(String language) throws MissingResourceException {
   public static String _(String s) {
     String res;
     try {
-      res = i18n.getString(s);
+      if (i18n == null)
+        res = s;
+      else
+        res = i18n.getString(s);
     } catch (MissingResourceException e) {
       res = s;
     }