[BUG]: pass parameters by const reference

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What version (or hash if on master) of pybind11 are you using?

pybind11/2.6.1

Problem description

when i pass a const reference from python to a c++ class, the m_ptr will be null later

Reproducible example code

class A {
const pybind11::array_t<int64_t>& data;

A(const pybind11::array_t<int64_t> data): data(data){}
}

can not work, while remove the const it is fine

class A {
pybind11::array_t<int64_t> data;

A(const pybind11::array_t<int64_t> data): data(data){}
}

Is this a regression? Put the last known working version here if it is.

Not a regression

The payload names no repository files or tests. Start by reproducing the pybind11 2.6.1 example with class A, comparing the const-reference member with the value member and observing when m_ptr becomes null. Done should establish the expected lifetime behavior and record the result in an appropriate regression test or issue clarification.