Fix more buttons being enabled/disabled issues

ViewModels/MainViewModel.cs

@@ -92,7 +92,15 @@ class MainViewModel : BaseViewModel, IFontResolver
     public ObservableCollection<ReportFile> ReportFiles
     {
         get => _reportFiles;
-        set { _reportFiles = value; NotifyPropertyChanged(); }
+        set 
+        { 
+            _reportFiles = value;
+            NotifyPropertyChanged(); 
+            _reportFiles.CollectionChanged += ( sender, e ) => 
+            { 
+                NotifyPropertyChanged(nameof(IsCreatePDFButtonEnabled)); 
+            };
+        }
     }
 
     private void LogInfo(string message, params object[]? arguments)
@@ -160,6 +168,7 @@ class MainViewModel : BaseViewModel, IFontResolver
                 ResortPDFItemsByDate();
             }
         }
+        NotifyPropertyChanged(nameof(IsCreatePDFButtonEnabled));
     }
     
     public void ShowAbout()

Views/MainView.axaml

@@ -151,7 +151,7 @@
         <StackPanel Orientation="Horizontal"
                     Spacing="4">
             <Button Command="{Binding AddItem}"
-                    IsEnabled="{Binding IsCreatePDFButtonEnabled}">
+                    IsEnabled="{Binding !IsCreatingPDF}">
                 <TextBlock><Run Text="&#x002b;" FontFamily="{StaticResource FontAwesomeSolid}"/> Add Item</TextBlock>
             </Button>
             <Button Command="{Binding SaveInterimReportInfo}"