check type before msgtype in the case of `m.sticker` with msgtype (undef)
check type before msgtype in the case of `m.sticker` with msgtype (undef)

Signed-off-by: Michael Telatynski <94c9867e567d21b48f1c67ccab9a43d4b4ded84f@gmail.com>

matrix-org/matrix-react-sdk,aperezdc/matrix-react-sdk,aperezdc/matrix-react-sdk,matrix-org/matrix-react-sdk,aperezdc/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,aperezdc/matrix-react-sdk,matrix-org/matrix-react-sdk