[Core] Fix removing groupable items when not grouped

Fixes #544

Author: Eric Maupin

Xamarin.PropertyEditing.Tests/PanelViewModelTests.cs

@@ -335,6 +335,35 @@ public void AddGroupedAtEnd ()
 			Assert.That (vm.ArrangedEditors.Any (g => g.Category == "ints"), Is.True, "Does not have grouped editors category");
 		}
 
+		[Test]
+		[Description ("#544 Bug coverage for removing groupable items when not grouped")]
+		public void FilterGroupableWhenNotGrouped ()
+		{
+			var stringProvider = new StringViewModelTests ();
+
+			var stringProperty1 = stringProvider.GetPropertyMock ("string1");
+			var stringProperty2 = stringProvider.GetPropertyMock ("string2");
+
+			var editor = new MockObjectEditor (stringProperty1.Object, stringProperty2.Object);
+
+			var provider = new Mock<IEditorProvider> ();
+			provider.Setup (p => p.GetObjectEditorAsync (editor.Target)).ReturnsAsync (editor);
+
+			var platform = new TargetPlatform (provider.Object) {
+				GroupedTypes = new Dictionary<Type, string> {
+					{ typeof(string), "B" }
+				}
+			};
+
+			var vm = new PanelViewModel (platform);
+			Assume.That (vm.ArrangeMode, Is.EqualTo (PropertyArrangeMode.Name));
+			vm.SelectedObjects.Add (editor.Target);
+			Assume.That (vm.ArrangedEditors[0].Editors.Count, Is.EqualTo (2));
+
+			vm.FilterText = "A";
+			Assert.That (vm.ArrangedEditors.Count, Is.EqualTo (0));
+		}
+
 		[Test]
 		public async Task AutoExpand ()
 		{

Xamarin.PropertyEditing/ViewModels/PanelViewModel.cs

@@ -58,7 +58,7 @@ public bool Remove (EditorViewModel editor)
 
 			var list = GetList (editor, separate: true);
 			if (editor is PropertyViewModel pvm && this.targetPlatform.GroupedTypes != null && this.targetPlatform.GroupedTypes.TryGetValue (pvm.Property.Type, out string groupName)) {
-				var group = list.OfType<PropertyGroupViewModel> ().First (gvm => gvm.Category == groupName);
+				var group = list.OfType<PropertyGroupViewModel> ().FirstOrDefault (gvm => gvm.Category == groupName);
 				if (group != null) {
 					bool found = group.Remove (pvm);
 					if (!group.HasChildElements)