GuestDocument - Page create - Bugfix

Fixed a bug that caused exceptions when "Create New" button was clicked before searching if GuestDocument already exists.

src/Somnia.GuestLog/Components/Pages/GuestDocuments/GuestDocNew.razor

@@ -18,10 +18,13 @@
 <MudStack Row="true" Class="my-4">
     <MudText Typo="Typo.h4" GutterBottom="true">New Guest Document</MudText>
     <MudSpacer />
-    <MudButton Variant="Variant.Filled" Color="Color.Success" Size="Size.Small" StartIcon="@Icons.Material.Filled.Add"
-               OnClick="() => BtnSaveNewGuest()">
-        @LanguageLocale.general_btnCreate
-    </MudButton>
+    @if (currentPageMode == ePageMode.createNew)
+    {
+        <MudButton Variant="Variant.Filled" Color="Color.Success" Size="Size.Small" StartIcon="@Icons.Material.Filled.Add"
+                   OnClick="() => BtnSaveNewGuest()">
+            @LanguageLocale.general_btnCreate
+        </MudButton>
+    }
     <MudButton Variant="Variant.Filled" Color="Color.Default" Size="Size.Small"
                StartIcon="@Icons.Material.Filled.ArrowBack" OnClick="() => BtnReturn()">
         @LanguageLocale.general_btnReturn
@@ -129,6 +132,8 @@
 
     private async Task BtnSaveNewGuest()
     {
+        Debug.Assert(currentPageMode == ePageMode.createNew && _form != null);
+
         bool isFormValid = await _form.ValidateForm();
         if (!isFormValid)
         {