Make fields optional

library.json

@@ -3,7 +3,7 @@
   "contentType": "question",
   "majorVersion": 1,
   "minorVersion": 0,
-  "patchVersion": 13,
+  "patchVersion": 14,
   "runnable": 1,
   "machineName": "H5P.QuestionSet",
   "author": "Amendor AS",

semantics.json

@@ -141,6 +141,7 @@
         "label": "Quiz passed title",
         "placeholder": "Congratulations!",
         "default": "Congratulations!",
+        "optional": true,
         "description": "This title will be displayed above results if the user has successfully passed the quiz."
       },
       {
@@ -149,6 +150,7 @@
         "widget": "textarea",
         "label": "Passed comment",
         "default": "You did very well!",
+        "optional": true,
         "description": "This comment will be displayed after the score if the user has successfully passed the quiz."
       },
       {
@@ -156,6 +158,7 @@
         "type": "text",
         "label": "Quiz failed title",
         "default": "Oh, no!",
+        "optional": true,
         "description": "This title will be displayed above the results if the user has failed the quiz."
       },
       {
@@ -164,6 +167,7 @@
         "widget": "textarea",
         "label": "Failed comment",
         "default": "This didn't go so well.",
+        "optional": true,
         "description": "This comment will be displayed after the score if the user has failed the quiz."
       },
       {