$result->fetch_assoc() is failing

I see it that part of the manual. My result is this:

mysqli_result Object
(
[current_field] => 0
[field_count] => 10
[lengths] =>
[num_rows] => 6
[type] => 0
)

But the $result_array is [0]. The question is why would fetch_assoc() error out rather than return some type of return code?

proof that an old dog can learn new tricks