Allow regular users to unlink tags from photos.

controllers/ViewPhoto.php

@@ -98,8 +98,19 @@ class ViewPhoto extends HTMLController
 		}
 
 		// We are!
-		$photo->linkTags([(int) $_POST['id_tag']]);
-		echo json_encode(['success' => true]);
-		exit;
+		if (!isset($_POST['delete']))
+		{
+			$photo->linkTags([(int) $_POST['id_tag']]);
+			echo json_encode(['success' => true]);
+			exit;
+		}
+
+		// ... deleting, that is.
+		else
+		{
+			$photo->unlinkTags([(int) $_POST['id_tag']]);
+			echo json_encode(['success' => true]);
+			exit;
+		}
 	}
 }