fix app back button on empty history

Author: Fiery-132

src/routes/AppHeader.svelte

@@ -36,8 +36,11 @@
     <!-- svelte-ignore a11y_consider_explicit_label -->
     <button
       on:click={canGoBack
-        ? () => window.history.back()
-        : () => goto("/app/home")}
+        ? () =>
+            window.history.length > 1
+              ? window.history.back()
+              : goto("/app/home")
+        : undefined}
       class:opacity-0={!canGoBack}
       class="-m-4 p-4"
     >