I decided to use an accessor now, iterating over the tensor elements and comparing & setting where necessary. May not be elegant but solves the problem at hand for now. Code is like:
auto a = t.accessor<float, 1>();
		
for(int i=0; i<a.size(0); i++)
	if(a[i] == 0.0)
		a[i] = 1.0;

Thanks for your help!  )