PdeKeyListener.java: tab key behaves correctly if !editor.tabs.expand

If the `editor.tabs.expand` preference setting is set to `false` (tabs 
are *not* expanded to spaces), insert a tab character when the tab key 
is pressed. Previously nothing would be inserted.

app/src/processing/mode/java/PdeKeyListener.java

@@ -194,6 +194,9 @@ public class PdeKeyListener {
         textarea.setSelectedText(spaces(tabSize));
         event.consume();
         return true;
+      } else if (!Preferences.getBoolean("editor.tabs.expand")) {
+        textarea.setSelectedText("\t");
+        event.consume();
       }
       break;