Add null check for prefab editor

Scripts/SoftMask.cs

@@ -340,7 +340,10 @@ namespace Coffee.UIExtensions
 		{
 			foreach (var sm in s_ActiveSoftMasks)
 			{
-				sm.UpdateMaskTexture();
+				if(sm)
+				{
+					sm.UpdateMaskTexture ();
+				}
 			}
 		}
 

Scripts/SoftMaskable.cs

@@ -158,11 +158,14 @@ namespace Coffee.UIExtensions
 		
 			foreach (var sm in s_ActiveSoftMaskables)
 			{
-				Material mat = sm._maskMaterial;
+				if(sm)
-				if (mat)
 				{
-					mat.SetMatrix("_SceneView", w2c);
+					Material mat = sm._maskMaterial;
-					mat.SetMatrix("_SceneProj", prj);
+					if (mat)
+					{
+						mat.SetMatrix ("_SceneView", w2c);
+						mat.SetMatrix ("_SceneProj", prj);
+					}
 				}
 			}
 		}