Fix errors with creating gas mixtures on class instantiation (#1916)

* Fix errors when gas mixtures are created on class instantiation

* Fix mistake

Content.Server/GameObjects/Components/Body/Respiratory/LungComponent.cs

@@ -21,7 +21,7 @@ namespace Content.Server.GameObjects.Components.Body.Respiratory
         /// </summary>
         [ViewVariables(VVAccess.ReadWrite)] private float Pressure { get; set; }
 
-        [ViewVariables] public GasMixture Air { get; set; } = new GasMixture();
+        [ViewVariables] public GasMixture Air { get; set; }
 
         [ViewVariables] public LungStatus Status { get; set; }
 
@@ -29,6 +29,8 @@ namespace Content.Server.GameObjects.Components.Body.Respiratory
         {
             base.ExposeData(serializer);
 
+            Air = new GasMixture();
+
             serializer.DataReadWriteFunction(
                 "volume",
                 6,