ctf: silence some -Wnull-dereference errors

ctf: silence some -Wnull-dereference errors

Building with gcc 14.1.1 (Arch Linux package 14.1.1+r58+gfc9fb69ad62-1),
I get some `-Wnull-dereference` errors that seem bogus:

      CXX      plugins/ctf/fs-src/fs.lo
    In file included from /usr/include/c++/14.1.1/memory:78,
                     from /home/simark/src/babeltrace/src/cpp-common/bt2c/glib-up.hpp:10,
                     from /home/simark/src/babeltrace/src/plugins/ctf/fs-src/fs.cpp:19:
    In member function 'std::__uniq_ptr_impl<_Tp, _Dp>::pointer std::__uniq_ptr_impl<_Tp, _Dp>::release() [with _Tp = ctf_fs_trace; _Dp = std::default_delete<ctf_fs_trace>]',
        inlined from 'std::__uniq_ptr_impl<_Tp, _Dp>& std::__uniq_ptr_impl<_Tp, _Dp>::operator=(std::__uniq_ptr_impl<_Tp, _Dp>&&) [with _Tp = ctf_fs_trace; _Dp = std::default_delete<ctf_fs_trace>]' at /usr/include/c++/14.1.1/bits/unique_ptr.h:185:7,
        inlined from 'std::__uniq_ptr_data<_Tp, _Dp, <anonymous>, <anonymous> >& std::__uniq_ptr_data<_Tp, _Dp, <anonymous>, <anonymous> >::operator=(std::__uniq_ptr_data<_Tp, _Dp, <anonymous>, <anonymous> >&&) [with _Tp = ctf_fs_trace; _Dp = std::default_delete<ctf_fs_trace>; bool <anonymous> = true; bool <anonymous> = true]' at /usr/include/c++/14.1.1/bits/unique_ptr.h:237:24,
        inlined from 'std::unique_ptr<_Tp, _Dp>& std::unique_ptr<_Tp, _Dp>::operator=(std::unique_ptr<_Tp, _Dp>&&) [with _Tp = ctf_fs_trace; _Dp = std::default_delete<ctf_fs_trace>]' at /usr/include/c++/14.1.1/bits/unique_ptr.h:408:19,
        inlined from 'int ctf_fs_component_create_ctf_fs_trace(ctf_fs_component*, bt2::ConstArrayValue, const char*, bt_self_component*)' at /home/simark/src/babeltrace/src/plugins/ctf/fs-src/fs.cpp:1415:44:
    /usr/include/c++/14.1.1/bits/unique_ptr.h:211:17: error: potential null pointer dereference [-Werror=null-dereference]
      211 |         pointer __p = _M_ptr();
          |                 ^~~

      CXX      plugins/ctf/lttng-live/viewer-connection.lo
    In file included from /usr/include/c++/14.1.1/bits/stl_tempbuf.h:61,
                     from /usr/include/c++/14.1.1/memory:66,
                     from /home/simark/src/babeltrace/src/cpp-common/bt2s/make-unique.hpp:10,
                     from /home/simark/src/babeltrace/src/plugins/ctf/lttng-live/viewer-connection.cpp:16:
    In function 'void std::_Construct(_Tp*, _Args&& ...) [with _Tp = char; _Args = {}]',
        inlined from 'static _ForwardIterator std::__uninitialized_default_n_1<true>::__uninit_default_n(_ForwardIterator, _Size) [with _ForwardIterator = char*; _Size = long unsigned int]' at /usr/include/c++/14.1.1/bits/stl_uninitialized.h:666:23,
        inlined from 'static _ForwardIterator std::__uninitialized_default_n_1<true>::__uninit_default_n(_ForwardIterator, _Size) [with _ForwardIterator = char*; _Size = long unsigned int]' at /usr/include/c++/14.1.1/bits/stl_uninitialized.h:660:9,
        inlined from '_ForwardIterator std::__uninitialized_default_n(_ForwardIterator, _Size) [with _ForwardIterator = char*; _Size = long unsigned int]' at /usr/include/c++/14.1.1/bits/stl_uninitialized.h:712:20,
        inlined from '_ForwardIterator std::__uninitialized_default_n_a(_ForwardIterator, _Size, allocator<_Tp>&) [with _ForwardIterator = char*; _Size = long unsigned int; _Tp = char]' at /usr/include/c++/14.1.1/bits/stl_uninitialized.h:779:44,
        inlined from 'void std::vector<_Tp, _Alloc>::_M_default_append(size_type) [with _Tp = char; _Alloc = std::allocator<char>]' at /usr/include/c++/14.1.1/bits/vector.tcc:863:35,
        inlined from 'void std::vector<_Tp, _Alloc>::resize(size_type) [with _Tp = char; _Alloc = std::allocator<char>]' at /usr/include/c++/14.1.1/bits/stl_vector.h:1016:21,
        inlined from 'lttng_live_get_one_metadata_status lttng_live_get_one_metadata_packet(lttng_live_trace*, std::vector<char>&)' at /home/simark/src/babeltrace/src/plugins/ctf/lttng-live/viewer-connection.cpp:1028:16:
    /usr/include/c++/14.1.1/bits/stl_construct.h:119:7: error: null pointer dereference [-Werror=null-dereference]
      119 |       ::new((void*)__p) _Tp(std::forward<_Args>(__args)...);
          |       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Silence the warning at these specific spots to get the build going.

Change-Id: Ia46b4f420cfdd00202d0b915825ac3b995128291
Signed-off-by: Simon Marchi <simon.marchi@efficios.com>
Reviewed-on: https://review.lttng.org/c/babeltrace/+/12776
Reviewed-by: Philippe Proulx <eeppeliteloop@gmail.com>
Tested-by: jenkins <jenkins@lttng.org>