[analogwzrd]

Some others have mentioned this in their comments and I agree that once you succeed in getting a non-null result, publishing the null results (all the things you tried that didn't work) could be included as appendices or something.

Also, just because you get a null result doesn't mean that nothing was learned, that something new (and unexpected) wasn't stumbled on, or that some innovation didn't happen.

There are tiers of publications and journals. Even if you get a null result and you're not going to get it accepted in Nature, it's very possible that you can get a conference paper (sometimes peer reviewed) out of something that was learned.