in extjs 5/6 there is a caching issue, where they
save dom elements for reuse, but the garbage collector
can set them to null
when the framework now reuses the "cached" element it is null,
and any action on it produces an error, which breaks the site
for details see the forum link in the comment
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
