do similar array copy at end of recursion

internal/statsapi/feed.go

@@ -54,11 +54,14 @@ func patch(obj any, path string, value any) error {
 				break
 			}
 
-			if idx < len(v) {
-				v[idx] = value
-			} else {
-				v = append(v, value)
+			if len(v) <= idx {
+				arr := make([]any, idx+1)
+				for i, val := range v {
+					arr[i] = val
+				}
+				v = arr
 			}
+			v[idx] = value
 		default:
 			err = errors.New("couldn't determine type")
 		}