Do not try to request thumbnails with non-integer sizes
Issue described in: https://github.com/vector-im/riot-web/issues/9690
matrix-react-sdk was patched separately, so that it won't call `mxcUrlToHttp()`
(and in turn `getHttpUriForMxc()`) with non-integer sizes.
This patch fixes the JS SDK as well, hoping to prevent the same issue
from happening on other clients (besides matrix-react-sdk / riot-web).
Signed-off-by: Slavi Pantaleev <slavi@devture.com>
