Try to fix SharedMouthStorageSystem (ss14Starlight#4789)

## Short description

Asserts StorageComponent.Container isn't null.

## Why we need to add this
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Discussions as well as Bug Reports here. Please describe how this will
change the game balance. -->

Seeing some hard-to-reproduce bugs in prod, this seems the most likely
culprit.

## Media (Video/Screenshots)
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of the changes.
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N/a

## Checks
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- [x] I do not require assistance to complete the PR.
- [ ] Before posting/requesting review of a PR, I have verified that the
changes work.
- [x] I have added screenshots/videos of the changes, or this PR does
not change in-game mechanics.
- [x] I affirm that my changes are licensed under the [MIT
License](https://github.com/ss14Starlight/space-station-14/blob/Starlight/LICENSE.TXT)
and grant permission for use in this repository under its conditions.

No guarantee this works so no CL

Author: redmushie

Content.Shared/_Starlight/Storage/SharedMouthStorageSystem.cs

@@ -32,7 +32,9 @@ public override void Initialize()
 
     protected bool IsMouthBlocked(MouthStorageComponent component)
     {
-        if (!TryComp<StorageComponent>(component.MouthId, out var storage))
+        // ReSharper disable once ConditionIsAlwaysTrueOrFalseAccordingToNullableAPIContract
+        if (!TryComp<StorageComponent>(component.MouthId, out var storage) ||
+            storage.Container == null)
             return false;
 
         return storage.Container.ContainedEntities.Count > 0;
@@ -71,11 +73,11 @@ private void OnExamined(EntityUid uid, MouthStorageComponent component, Examined
     /// </summary>
     private void SpitOutMouth(EntityUid uid, MouthStorageComponent component)
     {
-        if (component.MouthId == null)
-            return;
-
-        if (!TryComp<StorageComponent>(component.MouthId.Value, out var storage)
-            || storage.Container.ContainedEntities.Count == 0)
+        // ReSharper disable once ConditionIsAlwaysTrueOrFalseAccordingToNullableAPIContract
+        if (component.MouthId == null ||
+            !TryComp<StorageComponent>(component.MouthId.Value, out var storage) ||
+            storage.Container == null ||
+            storage.Container.ContainedEntities.Count == 0)
             return;
 
         var dumpQueue = _container.EmptyContainer(storage.Container, true, Transform(uid).Coordinates);