What precaution should be taken when dealing with a cracked inner window?

When dealing with a cracked inner window, it's crucial to verify that the heat switch is off. This precaution is important because if the heat is applied to a cracked window, it can exacerbate the damage, potentially leading to a complete failure of the window. The heat could cause further expansion of the crack, or the increased temperature could create additional stress on the glass, making it shatter or break completely. Ensuring that the heat switch is off minimizes this risk and helps maintain safety for all onboard.

While the other options involve safety measures relevant to various situations, they do not specifically address the immediate concerns associated with handling a cracked inner window, which is primarily about preventing further damage and maintaining structural integrity.