clang-static-analyzer: Dereference of null pointer in any_executor.hpp

[rohansuri]

Hello,
Thank you for the wonderful library. I am using it for a http client. However, I see clang-analyzer report the following issue.

boost version: 1.82.0
clang-version: 9.0.0

scan-build: Using '/usr/local/bin/clang-9' for static analysis
The C compiler identification is Clang 9.0.0
The CXX compiler identification is Clang 9.0.0

File name: include/boost/asio/execution/any_executor.hpp
Line number: 1931
Code snippet:

template <typename Property>
1925 | any_executor prefer(const Property& p,
1926 | typename enable_if<
1927 | find_convertible_preferable_property<Property>::value
1928 | >::type* = 0) const
1929 | {
1930 | typedef find_convertible_preferable_property<Property> found;
1931 | return prop_fns_[found::index].prefer(object_fns_->target(*this),
1932 | &static_cast<const typename found::type&>(p));
1933 | }

Exact error reported in scan report:

Access to field 'target' results in a dereference of a null pointer (loaded from field 'object_fns_')

Warning emitted during the build itself:

In file included from include/boost/asio.hpp:20:
In file included from include/boost/asio/any_completion_executor.hpp:22:
In file included from include/boost/asio/execution.hpp:19:
include/boost/asio/execution/any_executor.hpp:1931:43: warning: Access to field 'target' results in a dereference of a null pointer (loaded from field 'object_fns_')
return prop_fns_[found::index].prefer(object_fns_->target(*this),
                                           ^~~~~~~~~~~~~~~~~~~
1 warning generated.