fix: wrap if-return with block statement to satisfy useBlockStatements lint rule

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: github-actions[bot]

src/core/series.ts

@@ -764,7 +764,7 @@ export class Series<T extends Scalar = Scalar> {
     const hit = ascending
       ? (naLast ? this._svCacheAL : this._svCacheAF)
       : (naLast ? this._svCacheDL : this._svCacheDF);
-    if (hit !== null) return hit;
+    if (hit !== null) { return hit; }
 
     const n = this._values.length;
     const vals = this._values;