Fix critical table selector disabled state

src/RolemasterDb.App/Components/Pages/Tables.razor

@@ -20,7 +20,7 @@
             class="input-shell"
             value="@selectedTableSlug"
             @onchange="HandleTableChanged"
-            disabled="@isReferenceDataLoading || (referenceData?.CriticalTables.Count ?? 0) == 0">
+            disabled="@IsTableSelectionDisabled">
             @if (referenceData is null)
             {
                 <option value="">Loading tables...</option>
@@ -176,6 +176,7 @@
     private bool isReferenceDataLoading = true;
     private string? detailError;
     private Dictionary<(string RollBand, string? GroupKey, string ColumnKey), CriticalTableCellDetail>? cellIndex;
+    private bool IsTableSelectionDisabled => isReferenceDataLoading || (referenceData?.CriticalTables.Count ?? 0) == 0;
 
     protected override async Task OnInitializedAsync()
     {