Fix complex form test - this one should fail

The Components property on a complex form can contain empty GUIDs for
the complex form entry ID, because we can infer that (it's the entry
we're looking at right now). But it cannot contain an empty GUID for the
component entry ID, because that's meaningless: which component is being
referenced is the whole point of the Components property.

backend/FwLite/MiniLcm.Tests/Validators/EntryValidatorTests.cs

@@ -128,11 +128,11 @@ public void Succeeds_WhenComplexFormsContainEmptyGuid()
     }
 
     [Fact]
-    public void Succeeds_WhenComponentsContainEmptyGuid()
+    public void Fails_WhenComponentsContainEmptyGuid()
     {
         var entryId = Guid.NewGuid();
         var entry = new Entry() { Id = entryId, LexemeForm = new MultiString(){{"en", "lexeme"}}, Components = [new ComplexFormComponent(){ ComplexFormEntryId = entryId, ComponentEntryId = Guid.Empty }] };
-        _validator.TestValidate(entry).ShouldNotHaveAnyValidationErrors();
+        _validator.TestValidate(entry).ShouldHaveValidationErrorFor("Components[0]");
     }
 
     private void SetProperty(Entry entry, string propName, string content)

backend/FwLite/MiniLcm/Validators/EntryValidator.cs

@@ -13,6 +13,7 @@ public EntryValidator()
         RuleFor(e => e.LiteralMeaning).NoEmptyValues();
         RuleFor(e => e.Note).NoEmptyValues();
         RuleForEach(e => e.Senses).SetValidator(entry => new SenseValidator(entry));
+        RuleForEach(e => e.Components).Must(NotBeEmptyComponentReference);
         RuleForEach(e => e.Components).Must(NotBeComponentSelfReference);
         RuleForEach(e => e.Components).Must(HaveCorrectComponentEntryReference);
         RuleForEach(e => e.ComplexForms).Must(NotBeComplexFormSelfReference);
@@ -23,13 +24,19 @@ public EntryValidator()
         RuleForEach(e => e.ComplexFormTypes).SetValidator(new ComplexFormTypeValidator());
     }
 
+    private bool NotBeEmptyComponentReference(Entry entry, ComplexFormComponent component)
+    {
+        return component.ComponentEntryId != Guid.Empty;
+    }
+
     private bool NotBeComponentSelfReference(Entry entry, ComplexFormComponent component)
     {
-        return component.ComponentEntryId != entry.Id || component.ComponentEntryId == Guid.Empty;
+        return component.ComponentEntryId != entry.Id;
     }
 
     private bool HaveCorrectComponentEntryReference(Entry entry, ComplexFormComponent component)
     {
+        // Empty GUID is okay here because it can be guessed from the parent object
         return component.ComplexFormEntryId == entry.Id || component.ComplexFormEntryId == Guid.Empty;
     }
 
@@ -40,6 +47,7 @@ private bool NotBeComplexFormSelfReference(Entry entry, ComplexFormComponent com
 
     private bool HaveCorrectComplexFormEntryReference(Entry entry, ComplexFormComponent component)
     {
+        // Empty GUID is okay here because it can be guessed from the parent object
         return component.ComponentEntryId == entry.Id || component.ComponentEntryId == Guid.Empty;
     }
 }