Refactor to enforce strictNullChecks

This commit applies `strictNullChecks` to the entire codebase to improve
maintainability and type safety. Key changes include:

- Remove some explicit null-checks where unnecessary.
- Add necessary null-checks.
- Refactor static factory functions for a more functional approach.
- Improve some test names and contexts for better debugging.
- Add unit tests for any additional logic introduced.
- Refactor `createPositionFromRegexFullMatch` to its own function as the
  logic is reused.
- Prefer `find` prefix on functions that may return `undefined` and
  `get` prefix for those that always return a value.

src/presentation/components/Scripts/View/Tree/NodeContent/Reverter/CategoryReverter.ts

@@ -25,10 +25,7 @@ export class CategoryReverter implements IReverter {
 }
 
 function getAllSubScriptReverters(categoryId: number, collection: ICategoryCollection) {
-  const category = collection.findCategory(categoryId);
-  if (!category) {
-    throw new Error(`Category with id "${categoryId}" does not exist`);
-  }
+  const category = collection.getCategory(categoryId);
   const scripts = category.getAllScriptsRecursively();
   return scripts.map((script) => new ScriptReverter(script.id));
 }