Fix for #123: Add-SPOFile with Checkout option does not update existi…

…ng files in a library which has the Require Checkout -option set

Commands/Web/AddFile.cs

@@ -66,6 +66,7 @@ protected override void ExecuteCmdlet()
                 try
                 {
                     var existingFile = SelectedWeb.GetFileByServerRelativeUrl(fileUrl);
+                    existingFile.EnsureProperty(f => f.Exists);
                     if (existingFile.Exists)
                     {
                         SelectedWeb.CheckOutFile(fileUrl);