[scrollpastend addon] Work around potential infinite event-handler recursion

See https://discuss.codemirror.net/t/range-error-with-scrollpastend-addon/773

addon/scroll/scrollpastend.js

@@ -40,7 +40,9 @@
     if (cm.state.scrollPastEndPadding != padding) {
       cm.state.scrollPastEndPadding = padding;
       cm.display.lineSpace.parentNode.style.paddingBottom = padding;
+      cm.off("refresh", updateBottomMargin);
       cm.setSize();
+      cm.on("refresh", updateBottomMargin);
     }
   }
 });