Merged PR 164: Clear the leftover TODOs

- Remove nullable type from container.properties.parentId
- Add Swal when trying to delete main container
- Moved default editor state to default.ts
- Moved default symbol model to default.ts

src/Components/Editor/Actions/ContainerOperations.ts

@@ -9,6 +9,7 @@ import { IAvailableContainer } from '../../../Interfaces/IAvailableContainer';
 import { GetDefaultContainerProps, DEFAULTCHILDTYPE_ALLOW_CYCLIC, DEFAULTCHILDTYPE_MAX_DEPTH } from '../../../utils/default';
 import { ApplyBehaviors } from '../Behaviors/Behaviors';
 import { ISymbolModel } from '../../../Interfaces/ISymbolModel';
+import Swal from 'sweetalert2';
 
 /**
  * Select a container
@@ -64,7 +65,11 @@ export function DeleteContainer(
   if (container === mainContainerClone ||
     container.parent === undefined ||
     container.parent === null) {
-    // TODO: Implement alert
+    Swal.fire({
+      title: 'Oops...',
+      text: 'Deleting the main container is not allowed!',
+      icon: 'error'
+    });
     throw new Error('[DeleteContainer] Tried to delete the main container! Deleting the main container is not allowed!');
   }