:bug: removed existing targets from potential new target postitions

CMakeLists.txt

@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.27)
-project(Snake VERSION 1.0.0.0)
+project(Snake VERSION 1.1.0.0)
 
 set(CMAKE_CXX_STANDARD 23)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)

game/PlayingState.cxx

@@ -214,6 +214,9 @@ bool PlayingState::place_target()
   for (auto const& particle: tail_) {
     field.erase(particle);
   }
+  for (auto const& target: target_) {
+    field.erase(target);
+  }
 
   if (field.empty()) {
     return false;