fix: dropping card on firefox shouldn't redirect the user anymore

assets/js/landing.js

@@ -140,6 +140,9 @@ window.cardDrop = function(event) {
         rebuild_cards();
     }
     refresh_drop_to_add_button();
+
+    if (event.preventDefault) event.preventDefault();
+    if (event.stopPropagation) event.stopPropagation();
 }
 window.cardDropDiscard = function(event) {
     let serializedCard = event.dataTransfer.getData("card");
@@ -154,6 +157,8 @@ window.cardDropDiscard = function(event) {
         rebuild_cards();
     }
     refresh_drop_to_add_button();
+    if (event.preventDefault) event.preventDefault();
+    if (event.stopPropagation) event.stopPropagation();
 }
 window.allowDrop = function(event) {
     event.preventDefault();