any(L,3)
instead of my original answer
sum(L,3)>0
(Even if the result should be identical, there are some subtle differences, especially for edge cases.)
The reason is that Matlab might do some optimization, because it doesn't have to check all pages if the first already is true. This short-circuit evaluation has the potential of speeding up your code, especially for larger arrays. I don't know in which step sum will convert your array to a double, but it does somewhere along the line, which might tip you over the edge of needed memory for very large arrays.
original answer (to keep the record):
sum(L,3)>0
