Prevent chainpad issues to reset spreadsheets content

www/common/onlyoffice/inner.js

@@ -2166,6 +2166,12 @@ define([
                     url: newLatest.file
                 }, function () { });
                 newDoc = !content.hashes || Object.keys(content.hashes).length === 0;
+            } else if (!privateData.isNewFile) {
+                // This is an empty doc but not a new file: error
+                UI.errorLoadingScreen(Messages.unableToDisplay, false, function () {
+                    common.gotoURL('');
+                });
+                throw new Error("Empty chainpad for a non-empty doc");
             } else {
                 Title.updateTitle(Title.defaultTitle);
             }