Yes, there are null lambdas in C++!

null_lambda.cpp

// Lambda is a type of *value*, and *values* can’t be null.
// But y’know what can? *References* to values.

#include <functional>
#include <stdio.h>

const auto lambda = [] () -> const char* {
  return "Hello from lambda!";
};

void null_by_pointer(const decltype(lambda)* f) {
  puts(f ? (*f)() : "*f is null dereference!");
}

/** https://en.cppreference.com/w/cpp/utility/functional/function/operator_bool */
void null_by_std_function(std::function<const char*()> f) {
  puts(f ? f() : "f is empty!");
}

int main() {
  null_by_pointer(&lambda);
  null_by_pointer(nullptr);
  null_by_std_function(lambda);
  null_by_std_function(std::function<const char*()>()); // equivalent to std::function<…>(nullptr)
}