quic: Fix test which is always true

find_model_params() is first doing *nbuckets = 0; and it then checks
nbuckets for NULL. This is redundant as the dereferencing would cause a
segfault if nbuckets was NULL, so the if (nbuckets) test can't be false.
As Uri pointed out, the "/* bucket start */" comment on the same line
probably implies that the test was meant to be 'if (*nbuckets)'
I've ran a few test and I did not observe issues because of it...