[GENERIC viewer] Skip the `iframe`-case when checking if the `container` div, on `BaseViewer`-instances, is absolutely positioned (PR 12354 follow-up)
[GENERIC viewer] Skip the `iframe`-case when checking if the `container` div, on `BaseViewer`-instances, is absolutely positioned (PR 12354 follow-up)

Given that `getComputedStyle` only works on visible elements, the result of PR 12354 is that if the viewer is placed in a *hidden* `iframe` the viewer will now be broken. This obviously wasn't the intention of that PR, hence I believe that we should limit the `position: absolute;` check slightly to avoid this.

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