base: assert that stats bucket size is greater than 0

Change-Id: I9a2264e9ee74acea1f09f01ea8f5004567ba1ea8
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20049
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>
Tested-by: kokoro <noreply+kokoro@google.com>
1 file changed