Evict execution context from cache when there is no workflow defination found.

Author: lihannan99

internal/internal_task_handlers.go

@@ -616,6 +616,10 @@ func (wth *workflowTaskHandlerImpl) ProcessWorkflowTask(
 
 	workflowContext, err := wth.getOrCreateWorkflowContext(task, historyIterator)
 	if err != nil {
+		// The WorkflowContext will be removed from the cache if an error is found
+		// in workflowContext.err when calling Unlock() method.
+		workflowContext.err = err
+		defer workflowContext.Unlock()
 		return nil, nil, err
 	}
 	defer workflowContext.Unlock()