Don't use uninitialized ps from BotAI_GetClientState

If BotAI_GetPlayerState returns qfalse, ps is untouched and in
some cases means uninitialized. So don't use it if not valid.

code/game/ai_main.c

@@ -990,8 +990,10 @@ int BotAI(int client, float thinktime) {
 	}
 
 	//retrieve the current client state
-	BotAI_GetClientState( client, &bs->cur_ps );
-
+	if (!BotAI_GetClientState(client, &bs->cur_ps)) {
+		BotAI_Print(PRT_FATAL, "BotAI: failed to get player state for player %d\n", client);
+		return qfalse;
+	}
 	//retrieve any waiting server commands
 	while( trap_BotGetServerCommand(client, buf, sizeof(buf)) ) {
 		//have buf point to the command and args to the command arguments