Merge pull request #4852 from tobixen/fix/keyboard-state-hotplug-crash

fix(keyboard-state): fix segfault on device hotplug removal

include/modules/keyboard_state.hpp

@@ -3,6 +3,7 @@
 #include <fmt/chrono.h>
 #include <gtkmm/label.h>
 
+#include <mutex>
 #include <set>
 #include <unordered_map>
 
@@ -41,6 +42,7 @@ class KeyboardState : public AModule {
 
   struct libinput* libinput_;
   std::unordered_map<std::string, struct libinput_device*> libinput_devices_;
+  std::mutex devices_mutex_;  // protects libinput_devices_
   std::set<int> binding_keys;
 
   util::SleeperThread libinput_thread_, hotplug_thread_;