Some provider have these annual contract to provide them with chance to review and make changes annual. Some have contract which is on-going and details how to give notice and how notice of change will be given.
For most provider, we have starting contract which evolves over time as we faced with situation we not considered in beginning. It might be your provider copied this contract from internet and not considered what policy is if someone leave mid-year. It also might be that they have limited knowledge of writing contract/own dayhome and so think that parent able to commit to full year.
Like you, they might not have noticed this missing from their contract if situation not arose yet - this could be if newer provider.
The only way to know what options are is to speak to your provider. We can only guess the intention behind it as can you. Just ask her how you submit your notice if your situation changes and how much notice is needed. Had you both lost your job 2 weeks into this contract, it not reasonable that you would have been obligated to continue paying for care for another 50 weeks at full cost. Ask her and go from there.
Any contract can be challenged in Small Claims Court. If she says that you must pay for full year, and you refuse, she can take your to court and you will get chance to explain to Judge why you think it unfair. But in most cases, a signed contract over rides everything else because it's your responsibility to make sure you understand and agree. However, if a Judge feels language wasn't clear or contract was unreasonable, they might rule in your favour.