Revert "app (gimprc): Delete dead assignment"

This reverts commit d6d2a0bbd1
and allows more than one unknown gimprc token again.

Fixes Bug 674096 - Strange behavior with gimprc

app/config/gimprc-unknown.c

@@ -115,7 +115,11 @@ gimp_rc_add_unknown_token (GimpConfig  *config,
   token->key   = g_strdup (key);
   token->value = g_strdup (value);
 
-  if (!last)
+  if (last)
+    {
+      last = g_slist_last (g_slist_append (last, token));
+    }
+  else
     {
       unknown_tokens = g_slist_append (NULL, token);