File kajaani-kombat-gcc11.patch of Package kajaani-kombat

These SDL_* return NULL on error, and gcc11/clang won't allow this.
https://bugs.gentoo.org/739086
Index: kajaani-kombat-0.7/client_net.cpp
===================================================================
--- kajaani-kombat-0.7.orig/client_net.cpp
+++ kajaani-kombat-0.7/client_net.cpp
@@ -31,13 +31,13 @@ client_tcpnet::client_tcpnet(IPaddress *
   assert (ret != -1);
 
   cond = SDL_CreateCond();
-  if (cond <0)
+  if (!cond)
     {
       fprintf (stderr, "Error creating cond variable\n");
       exit(2);
     }
   mutex = SDL_CreateMutex();
-  if (mutex < 0)
+  if (!mutex)
     {
       fprintf (stderr, "Error creating mutex\n");
       exit(2);
@@ -45,13 +45,13 @@ client_tcpnet::client_tcpnet(IPaddress *
 
   active = true;
   trans_th = SDL_CreateThread (&client_tcpnet::transf_func, (void *) this);
-  if (trans_th < 0)
+  if (!trans_th)
     {
       fprintf(stderr, "Error starting thread: %s\n", SDL_GetError());
       exit(2);
     }
   input_th = SDL_CreateThread (&client_tcpnet::input_func, (void *) this);
-  if (input_th < 0)
+  if (!input_th)
     {
       fprintf(stderr, "Error starting thread: %s\n", SDL_GetError());
       exit(2);
Index: kajaani-kombat-0.7/game_server.cpp
===================================================================
--- kajaani-kombat-0.7.orig/game_server.cpp
+++ kajaani-kombat-0.7/game_server.cpp
@@ -64,7 +64,7 @@ void game_server::init_net()
   
   // OK, init server thread to listen to clients
   con_th = SDL_CreateThread (&game_server::connection_accepter, (void *) this);
-  if (con_th < 0)
+  if (!con_th)
     {
       fprintf (stderr, "[SRV] Error starting thread: %s\n", SDL_GetError());
       exit(2);