Opening a document shows a spinner in the center of the web page

[stbergmann]

With richdocuments 9.0.4 and 9.0.5, opening a document (with a local test instance of Collabora Online) shows a spinner now in the center of the web page, that either (depending on circumstances that are unclear to me) disappears again shortly thereafter or stays on forever, even after the document got loaded successfully. No such spinner could be observed with richdocuments 9.0.3.

A theory is that this is related to 99e52d3 "fix(officeViewer): remove superfluous high z-index".