Describe the bug
When the Filter predicate on VectorSearchOptions<T> is a nullable, search fails with an exception.

activeOnly is defined as bool? activeOnly = null in the methods parameters. Since the if block already ensures its never null, I don't see any issue why that operation should fail.

Both activeOnly and activeOnly.Value result in the exception.

Only by changing the method declaration to bool activeOnly or bool activeOnly = true, read non-nullable, the query executes successfully.

Imho this is not an expected behaviour and should be fixed, as its a very common way to define predicates that way.

To Reproduce

        Expression<Func<Project, bool>>? filter = null;
        if (activeOnly is not null)
        {
            filter = project => project.IsActive == activeOnly;
        }
        VectorSearchOptions<Project> filterOptions = new()
        {
            Top = top,
            IncludeTotalCount = true,
            Filter = filter,
        };

Throws:

System.NotSupportedException
  HResult=0x80131515
  Message=Equality expression not supported by Qdrant
  Source=Microsoft.SemanticKernel.Connectors.Qdrant
  StackTrace:
   at Microsoft.SemanticKernel.Connectors.Qdrant.QdrantFilterTranslator.TranslateEqual(Expression left, Expression right, Boolean negated)
   at Microsoft.SemanticKernel.Connectors.Qdrant.QdrantFilterTranslator.Translate(Expression node)
   at Microsoft.SemanticKernel.Connectors.Qdrant.QdrantFilterTranslator.Translate(LambdaExpression lambdaExpression, IReadOnlyDictionary`2 storagePropertyNames)
   at Microsoft.SemanticKernel.Connectors.Qdrant.QdrantVectorStoreRecordCollection`1.d__32`1.MoveNext()

        Expression<Func<Project, bool>>? filter = null;
        if (activeOnly is not null)
        {
            filter = project => project.IsActive == activeOnly.Value;
        }
        VectorSearchOptions<Project> filterOptions = new()
        {
            Top = top,
            IncludeTotalCount = true,
            Filter = filter,
        };

Expected behavior
Operation to succeed.

Platform

• Language: C#
• Source: Nuget
  • Microsoft.SemanticKernel 1.47.0
  • Microsoft.SemanticKernel.Connectors.Ollama 1.47.0-alpha
  • Microsoft.SemanticKernel.Connectors.Qdrant 1.47.0-preview
• AI model: not applicable
• IDE: Visual Studio 2022
• OS: Windows 11, 24H2