Solve a problem where if you give a name for cell and the name doesn't exist you get a crash during world query in GUECS.

guecs.cpp

@@ -80,16 +80,12 @@ namespace guecs {
     dbc::check(good, "LEL parsing failed.");
 
     for(auto& [name, cell] : $parser.cells) {
-      auto ent = entity(name);
+      auto ent = init_entity(name);
       $world.set<lel::Cell>(ent, cell);
     }
   }
 
-  DinkyECS::Entity UI::entity(std::string name) {
-    if($name_ents.contains(name)) {
-      // already exists so just return it
-      return $name_ents.at(name);
-    } else {
+  DinkyECS::Entity UI::init_entity(std::string name) {
     auto entity = $world.entity();
     // this lets you look up an entity by name
     $name_ents.insert_or_assign(name, entity);
@@ -97,6 +93,11 @@ namespace guecs {
     $world.set<CellName>(entity, {name});
     return entity;
   }
+
+  DinkyECS::Entity UI::entity(std::string name) {
+    dbc::check($name_ents.contains(name),
+        fmt::format("GUECS entity {} does not exist. Forgot to init_entity?", name));
+    return $name_ents.at(name);
   }
 
   void UI::init() {

guecs.hpp

@@ -114,6 +114,7 @@ namespace guecs {
 
       void position(int x, int y, int width, int height);
       void layout(std::string grid);
+      DinkyECS::Entity init_entity(std::string name);
       DinkyECS::Entity entity(std::string name);
 
       inline lel::CellMap& cells() {