embedding_layer: guard against zeros

Author: OneAdder

src/nf/nf_embedding_layer_submodule.f90

@@ -34,6 +34,8 @@ pure module subroutine forward(self, input)
       index = input(i)
       if (index > size(self % weights, 1)) then
         index = 1
+      elseif (index == 0) then
+        index = 1
       end if
       self % output(i, :) = self % weights(index, :)
     end do