Reject replies when author is blocked by thread owner in Model\Item::insert

- Move user-level item permission to Model\Item::isAllowedByUser
- Add user-level check for comments on top-level item

src/Model/Contact/User.php

@@ -64,7 +64,7 @@ class User
 	{
 		$cdata = Contact::getPublicAndUserContacID($cid, $uid);
 		if (empty($cdata)) {
-			return;
+			return false;
 		}
 
 		$public_blocked = false;
@@ -127,7 +127,7 @@ class User
 	{
 		$cdata = Contact::getPublicAndUserContacID($cid, $uid);
 		if (empty($cdata)) {
-			return;
+			return false;
 		}
 
 		$public_ignored = false;