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/application/Parser/Script/Compiler/Expressions/Expression/ExpressionPositionFactory.ts

@@ -0,0 +1,16 @@
+import { ExpressionPosition } from './ExpressionPosition';
+
+export function createPositionFromRegexFullMatch(
+  match: RegExpMatchArray,
+): ExpressionPosition {
+  const startPos = match.index;
+  if (startPos === undefined) {
+    throw new Error(`Regex match did not yield any results: ${JSON.stringify(match)}`);
+  }
+  const fullMatch = match[0];
+  if (!fullMatch.length) {
+    throw new Error(`Regex match is empty: ${JSON.stringify(match)}`);
+  }
+  const endPos = startPos + fullMatch.length;
+  return new ExpressionPosition(startPos, endPos);
+}