Fix scrambled data in spreadsheets: disable 'undo'

www/common/onlyoffice/inner.js

@@ -775,6 +775,18 @@ define([
                     view: false
                 };
             });
+            // Add an history keeper user to show that we're never alone
+            var hkId = Util.createRandomInteger();
+            p.push({
+                id: hkId,
+                idOriginal: String(hkId),
+                username: "History",
+                indexUser: i,
+                connectionId: Hash.createChannelId(),
+                isCloseCoAuthoring:false,
+                view: false
+            });
+            i++;
             if (!myUniqueOOId) { myUniqueOOId = String(myOOId) + i; }
             p.push({
                 id: myUniqueOOId,