Fix message deletion

Author: grishka

src/main/java/smithereen/controllers/MailController.java

@@ -253,8 +253,8 @@ public void deleteMessage(User self, MailMessage message){
 
 	public void actuallyDeleteMessage(User self, MailMessage message, boolean deleteRelated){
 		try{
-			if(message.ownerID!=self.id && message.senderID!=self.id){
-				throw new IllegalArgumentException("This user can't delete this message");
+			if(message.ownerID!=self.id || message.senderID!=self.id){
+				throw new UserActionNotAllowedException("This user can't delete this message");
 			}
 			Set<Long> idsToDelete=new HashSet<>();
 			idsToDelete.add(message.id);

src/main/java/smithereen/routes/MailRoutes.java

@@ -253,7 +253,7 @@ public static Object delete(Request req, Response resp, Account self, Applicatio
 		}else{
 			origElementID="msgRow"+msg.getIdString();
 		}
-		if(msg.isUnread()){
+		if(msg.isUnread() && msg.senderID==self.user.id){
 			restoreHtml+=TextProcessor.substituteLinks(l.get(msg.to.size()>1 ? "restore_or_delete_for_peer_multi" : "restore_or_delete_for_peer",
 					Map.of("name", ctx.getUsersController().getUserOrThrow(msg.getFirstRecipientID()).getFirstAndGender())),
 					Map.of(