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A completely blank page may be due to different causes, but it may represent a temporary crash. If that is the case, you should be able to see the Dashboard once again simply by refreshing (reloading) the page. If this does not work and you keep seeing only an empty page, please use the bug report page or the "Found a problem?" button on the Dashboard page, if you can see it.
When reporting the bug, please specify that you have already tried what suggested here and attach a screenshot.