Private field 'm_selection_active' is not used

[ExcaliburZero]

I was recently compiling minetest using the AUR build script minetest-git-leveldb and, while the program did compile correctly, there was a compiler error:

[ 48%] Building CXX object src/CMakeFiles/minetest.dir/guiFormSpecMenu.cpp.o
In file included from /home/chris/Programs/minetest-git-leveldb/src/minetest/src/guiFormSpecMenu.cpp:26:
/home/chris/Programs/minetest-git-leveldb/src/minetest/src/guiFormSpecMenu.h:404:20: warning: private field 'm_selection_active' is not used
      [-Wunused-private-field]
        bool              m_selection_active;
                          ^
1 warning generated.

I used GitHub's search function to look through the repository to see where that variable is used, and it looks like it is only used in the one file mentioned in the warning message.

I did a quick search of that file and it appears that the variable mentioned in the warning is not used any place other than it's declaration.

Is this variable unused? If so then it may be a good idea to remove it in order to get rid of the compiler warning.