Fixed #291 (readonly custom menus become non-readonly when block is edited)

byob.js

@@ -194,7 +194,7 @@ CustomBlockDefinition.prototype.prototypeInstance = function () {
                 part.fragment.type = slot[0];
                 part.fragment.defaultValue = slot[1];
                 part.fragment.options = slot[2];
-                part.fragment.isReadonly = slot[3] || false;
+                part.fragment.isReadOnly = slot[3] || false;
             }
         }
     });

history.txt

@@ -2069,3 +2069,4 @@ ______
 ------
 * Threads: Revert pull request #295 (xhr-headers), breaks existing installations
 * BYOB: Fixed #292 (pulldowns loose lines when exported as library)
+* BYOB: Fixed #291 (readonly custom menus become non-readonly when block is edited)