Fix subtle race condition with initializing new feature props

src/lib/draw/NewFeatureForm.svelte

@@ -1,17 +1,17 @@
 <script lang="ts" generics="F, S">
   import { type Config } from "$lib/config";
-  import { onDestroy, onMount } from "svelte";
+  import { onDestroy } from "svelte";
   import type { Schemes } from "$lib/draw/types";
   import type { Writable } from "svelte/store";
   import { featureProps } from "./stores";
 
   export let cfg: Config<F, S>;
   export let gjSchemes: Writable<Schemes<F, S>>;
 
-  // Always start with blank properties
-  onMount(() => {
-    $featureProps = {};
-  });
+  // Always start with blank properties. Run this immediately, NOT in onMount,
+  // to avoid racing with anything done in the editFeatureForm component.
+  $featureProps = {};
+
   onDestroy(() => {
     $featureProps = {};
   });