refactor: Move container cleaning code to a separate function

index.html

@@ -550,6 +550,12 @@
              fillCharacterRoster();
          };
 
+         const clearContainer = (cont) => {
+             while (cont.firstChild) {
+                 cont.removeChild(cont.lastChild);
+             }
+         };
+
          const fillCharacterRoster = () => {
              var characterIDs = Object.keys(characterRoster).toSorted((idA, idB) => {
                  // Sort by campaign name first
@@ -566,9 +572,7 @@
 
              var placeHolder = inpCharacterRoster.options[0];
 
-             while (inpCharacterRoster.firstChild) {
-                 inpCharacterRoster.removeChild(inpCharacterRoster.lastChild);
-             }
+             clearContainer(inpCharacterRoster);
 
              inpCharacterRoster.appendChild(placeHolder);