if the lineModel is nil, default to a none style.

Signed-off-by: Matt Bruce <matt.bruce@verizon.com>

MVMCoreUI/Atomic/Molecules/Items/TabsListItemModel.swift

@@ -78,6 +78,9 @@ public class TabsListItemModel: ListItemModel, ParentMoleculeModelProtocol {
         tabs = try typeContainer.decode(TabsModel.self, forKey: .tabs)
         molecules = try typeContainer.decodeModels2D(codingKey: .molecules)
         try super.init(from: decoder)
+        if line == nil {
+            self.line = LineModel(type: .none)
+        }
     }
     
     public override func encode(to encoder: Encoder) throws {