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

* Fix errors when gas mixtures are created on class instantiation

* Fix mistake

Content.IntegrationTests/Tests/Atmos/ConstantsTest.cs

@@ -4,6 +4,7 @@ using System.Threading.Tasks;
 using Content.Server.GameObjects.EntitySystems;
 using Content.Shared.Atmos;
 using NUnit.Framework;
+using Robust.Shared.GameObjects.Systems;
 
 namespace Content.IntegrationTests.Tests.Atmos
 {
@@ -18,10 +19,10 @@ namespace Content.IntegrationTests.Tests.Atmos
 
             await server.WaitIdleAsync();
 
-            var atmosSystem = server.ResolveDependency<AtmosphereSystem>();
-
             server.Post(() =>
             {
+                var atmosSystem = EntitySystem.Get<AtmosphereSystem>();
+
                 Assert.That(atmosSystem.Gases.Count(), Is.EqualTo(Atmospherics.TotalNumberOfGases));
 
                 Assert.That(Enum.GetValues(typeof(Gas)).Length, Is.EqualTo(Atmospherics.TotalNumberOfGases));

Content.Server/GameObjects/Components/Atmos/GasMixtureHolderComponent.cs

@@ -10,12 +10,14 @@ namespace Content.Server.GameObjects.Components.Atmos
     {
         public override string Name => "GasMixtureHolder";
 
-        [ViewVariables] public GasMixture GasMixture { get; set; } = new GasMixture();
+        [ViewVariables] public GasMixture GasMixture { get; set; }
 
         public override void ExposeData(ObjectSerializer serializer)
         {
             base.ExposeData(serializer);
 
+            GasMixture = new GasMixture();
+
             serializer.DataReadWriteFunction(
                 "volume",
                 0f,

Content.Server/GameObjects/Components/Body/Circulatory/BloodstreamComponent.cs

@@ -29,7 +29,7 @@ namespace Content.Server.GameObjects.Components.Body.Circulatory
         /// </summary>
         [ViewVariables] public ReagentUnit EmptyVolume => _internalSolution.EmptyVolume;
 
-        [ViewVariables] public GasMixture Air { get; set; } = new GasMixture(6);
+        [ViewVariables] public GasMixture Air { get; set; }
 
         [ViewVariables] public SolutionComponent Solution => _internalSolution;
 
@@ -45,6 +45,8 @@ namespace Content.Server.GameObjects.Components.Body.Circulatory
         {
             base.ExposeData(serializer);
 
+            Air = new GasMixture(6);
+
             serializer.DataField(ref _initialMaxVolume, "maxVolume", ReagentUnit.New(250));
         }
 

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,