fix from adspartan 1d8ba26a3a

noggit: texture_set: fix eraseUnusedTextures issue preventing from erasing textures when using the temp alphamaps and remove the correct texture

src/noggit/texture_set.cpp

@@ -233,8 +233,8 @@ void TextureSet::eraseTexture(size_t id)
     alphamaps[nTextures - 2] = std::nullopt;
   }
 
-  textures.erase(textures.begin()+id);
   nTextures--;
+  textures.erase(textures.begin() + nTextures);
 
   // erase the old info as a precaution but it's overriden when adding a new texture
   _layers_info[nTextures] = layer_info();
@@ -285,13 +285,14 @@ bool TextureSet::eraseUnusedTextures()
   {
     auto& amaps = tmp_edit_values.value();
 
-    for (int i = 0; i < 4096 && visible_tex.size() < nTextures; ++i)
+    for (int layer = 0; layer < nTextures && visible_tex.size() < nTextures; ++layer)
     {
-      for (int layer = 0; layer < nTextures; ++layer)
+      for (int i = 0; i < 4096; ++i)
       {
         if (amaps[layer][i] > 0.f)
         {
-          visible_tex.emplace(i);
+          visible_tex.emplace(layer);
+          break; // texture visible, go to the next layer
         }
       }
     }