Fix div by zero

src/targets/gpu/compile_gen.cpp

@@ -20,6 +20,10 @@ static std::vector<std::size_t> vector_sizes(const std::vector<shape>& inputs)
 
 vectorize vectorize::elements(std::size_t axis, const std::vector<shape>& inputs)
 {
+    if (std::all_of(inputs.begin(), inputs.end(), [&](const auto& s) {
+            return s.lens()[axis] == 1;
+        }))
+        return {1, axis};
     auto sizes = vector_sizes(inputs);
     std::vector<std::size_t> max_vec_size;
     std::transform(inputs.begin(),