ChessEngine: Gracefully handle GUI disconnections

Author: https://github.com/tcl3
Commit: 55347ed6a5
Pull-request: https://github.com/SerenityOS/serenity/pull/18140
Issue: https://github.com/SerenityOS/serenity/issues/17427
Reviewed-by: https://github.com/LucasChollet
Reviewed-by: https://github.com/petelliott

Userland/Services/ChessEngine/ChessEngine.cpp

@@ -68,3 +68,9 @@ void ChessEngine::handle_quit()
     if (on_quit)
         on_quit(ESUCCESS);
 }
+
+void ChessEngine::handle_unexpected_eof()
+{
+    if (on_quit)
+        on_quit(EPIPE);
+}

Userland/Services/ChessEngine/ChessEngine.h

@@ -19,6 +19,7 @@ public:
     virtual void handle_position(Chess::UCI::PositionCommand const&) override;
     virtual void handle_go(Chess::UCI::GoCommand const&) override;
     virtual void handle_quit() override;
+    virtual void handle_unexpected_eof() override;
 
     Function<void(int)> on_quit;