fix: remove excess return null

Author: aminya

lib/minimap.js

@@ -1118,14 +1118,13 @@ export default class Minimap {
 
   /**
    *  get the DecorationManagement API for the current minimapElement
-   * @return {DecorationManagement | null | undefined}
+   * @return {DecorationManagement | undefined}
    */
   getDecorationManagement() {
     if (!this.DecorationManagement) {
       if (this.minimapElement?.DecorationManagement) {
         this.DecorationManagement = this.minimapElement.DecorationManagement
       }
-      return null
     }
     return this.DecorationManagement
   }