BUGFIX: staff can now edit delted posts

fixes #1343

This was way easier than mucking with the UI

app/controllers/posts_controller.rb

@@ -59,7 +59,9 @@ def create
   def update
     params.require(:post)
 
-    post = Post.where(id: params[:id]).first
+    post = Post.where(id: params[:id])
+    post = post.with_deleted if guardian.is_staff?
+    post = post.first
     post.image_sizes = params[:image_sizes] if params[:image_sizes].present?
     guardian.ensure_can_edit!(post)
 

app/models/post_alert_observer.rb

@@ -49,6 +49,7 @@ def after_create_post_action(post_action)
   def after_create_post_revision(post_revision)
     post = post_revision.post
 
+    return unless post
     return if post_revision.user.blank?
     return if post_revision.user_id == post.user_id
     return if post.topic.private_message?