Fix puddle spilling properly (#4812)

Content.IntegrationTests/Tests/Fluids/PuddleTest.cs

@@ -214,8 +214,14 @@ namespace Content.IntegrationTests.Tests.Fluids
                 // Check that the puddle is unpaused
                 Assert.False(sPuddle.Owner.Paused);
 
-                // By now, the puddle should have evaporated and deleted.
+                // Check that the puddle has evaporated some of its volume
-                Assert.True(sPuddle.Deleted);
+                Assert.That(sPuddle.CurrentVolume, Is.LessThan(sPuddleStartingVolume));
+
+                // If its new volume is zero it should have been deleted
+                if (sPuddle.CurrentVolume == ReagentUnit.Zero)
+                {
+                    Assert.True(sPuddle.Deleted);
+                }
             });
         }
     }

Content.Shared/Chemistry/EntitySystems/SolutionContainerSystem.cs

@@ -50,9 +50,12 @@ namespace Content.Shared.Chemistry.EntitySystems
             foreach (var keyValue in component.Solutions)
             {
                 var solutionHolder = keyValue.Value;
-                solutionHolder.MaxVolume = solutionHolder.TotalVolume > solutionHolder.InitialMaxVolume
+                if (solutionHolder.MaxVolume == ReagentUnit.Zero)
-                    ? solutionHolder.TotalVolume
+                {
-                    : solutionHolder.InitialMaxVolume;
+                    solutionHolder.MaxVolume = solutionHolder.TotalVolume > solutionHolder.InitialMaxVolume
+                        ? solutionHolder.TotalVolume
+                        : solutionHolder.InitialMaxVolume;
+                }
 
                 UpdateAppearance(uid, solutionHolder);
             }