While every investors does need an emergency fund available for obvious reasons, you don't have to save up for emergency before you start investing, you can start with your investment first and then start saving for emergency situations later or you can do them simultaneously, and both funds should come from your discretionary funds so as to not disturb your necessary and basic expenses.
Emergency funds are like a fail-safe that helps to ensure your investment isn't disturbed during accumulation, it also makes provisions for situations like you losing your job, it helps keep an investor going until they secure another job and get their income flowing again all while keeping their investment intact.
I'm sure there are situations where investors had to sell the bitcoin stash early to take care of emergencies, it could be an accident and your insurance isn't coming early enough or it's not able to cover your expenses, it could also be a serious health condition that requires alot of money to treat, your emergency income accounts for and helps take care of these situations.
In this case, people's choices may vary. Some prefer to set up an emergency fund before they invest, but there are also those who immediately choose to invest and save up for their emergency fund while at it. However, this should not be an obstacle for someone to start investing in Bitcoin, because they can also invest in Bitcoin even before having an emergency fund. But they need to create an emergency fund as soon as possible because they just don't know when the situation will become unfavorable to them—having an emergency fund will greatly help them face unexpected situations without having to sell bitcoin at the wrong time.
An investor without an emergency and backup fund will find it very difficult to invest for a long-term, therefore it is important to have your emergency funds, not necessarily very huge amount in as much as it can meet up your needs when the need arises for it, its an extra fund, which you need to save within 3-4 months so that it can save your investment from being sold off before the time that you wish to sell it within your long-term journey.