v1.50.1 - libtmux bug fix

libtmux update

• py(deps) libtmux: 0.40.0 -> 0.40.1 by @tony in #956

  Bug fix for server environmental variables from tmux-python/libtmux#553.
  Thank you @ppentchev!

Full Changelog: v1.50.0...v1.50.1