ensure 304 response code does not throw

when working on microsoft/kiota#4190, we ensured 204 and other status codes with empty responses would not throw, we should do the same work for 304

Hi, I'd like to work on this. I'll submit a PR shortly.

Update: current main already contains this fix and a regression test from #460, which references a different issue. I’m withdrawing my claim to avoid a duplicate PR; this issue appears safe to close as already resolved.