Add validation before getting workflow in GenerateWorkflowInputAccessors

This commit introduces a validation check in the GenerateWorkflowInputAccessors handler before trying to get the workflow. This prevents any potential issues if the workflow execution context is not available or retrievable. The code flow now first attempts to get the workflow execution context and if it's not available, it will return a completed task.

src/modules/Elsa.CSharp/Handlers/GenerateWorkflowInputAccessors.cs

@@ -18,7 +18,11 @@ public Task HandleAsync(EvaluatingCSharp notification, CancellationToken cancell
     {
         var expressionExecutionContext = notification.Context;
         var workflowInputs = expressionExecutionContext.GetWorkflowInputs().ToList();
-        var workflow = expressionExecutionContext.GetWorkflowExecutionContext().Workflow;
+
+        if (!expressionExecutionContext.TryGetWorkflowExecutionContext(out var workflowExecutionContext))
+            return Task.CompletedTask;
+
+        var workflow = workflowExecutionContext.Workflow;
         var inputDefinitions = workflow.Inputs.ToList();
         var sb = new StringBuilder();
         sb.AppendLine("public partial class WorkflowInputsProxy {");