[iOS][MF] Remove extra loading indicator

Only add the loading indicator if the model hasn't been created

Bug: 912085
Change-Id: I0d557013eeb63cf882793460a342e22485fa48d5
Reviewed-on: https://chromium-review.googlesource.com/c/1363179Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Commit-Queue: Javier Ernesto Flores Robles <javierrobles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614299}

ios/chrome/browser/ui/autofill/manual_fill/fallback_view_controller.mm

@@ -65,8 +65,9 @@ constexpr float PopoverMaxHeight = 360;
   self.tableView.separatorInset = UIEdgeInsetsMake(0, 0, 0, 0);
   self.tableView.allowsSelection = NO;
   self.definesPresentationContext = YES;
-
-  [self startLoadingIndicatorWithLoadingMessage:@""];
+  if (!self.tableViewModel) {
+    [self startLoadingIndicatorWithLoadingMessage:@""];
+  }
 }
 
 - (void)presentDataItems:(NSArray<TableViewItem*>*)items {