How do I count to occurences of a number in an unsanitized array

Say I have cell A, with values:

0
0
1
[0; 1; 0]
1

Now I want to count the occurences of 1 is this matrix, and [0; 1; 0] should be ignored.

However, when I do:

amount_correct = sum(A == 1);

I get an error as soon as it arrives at [0; 1; 0].

I however simply want it to give as output 0 and move on to the next element of the array till I get to the end.

The eventual output should be 2.