how to check if variable exists in savefile or not?

hello
i want to check if the float array spawnposition exists in the save file before loading it, because my game keep freezing when i add new variable to savefile the first time and have to restart it everytime whenever i add new value to load, i need a if statement to check if that float exists in save file or not, anyone can help?

if(data.spawnposition != null)
{
spawnPoint.x = data.spawnposition[0];
spawnPoint.y = data.spawnposition[1];
spawnPoint.z = data.spawnposition[2];
}

for anyone who come across this issue i fixed it by checking if the float array is not null before assigning the values