fix(blocks): resolve variable display in mothership resource preview (#4226)

* fix(blocks): resolve variable display in mothership resource preview

Variables block showed empty assignments in the embedded workflow preview
because currentWorkflowId was read from URL params, which don't contain
workflowId in the mothership route. Fall back to activeWorkflowId from
the workflow registry.

* fix(blocks): narrow currentWorkflowId to string to satisfy strict null checks

Author: waleedlatif1

apps/sim/app/workspace/[workspaceId]/w/[workflowId]/components/workflow-block/workflow-block.tsx

@@ -862,8 +862,6 @@ export const WorkflowBlock = memo(function WorkflowBlock({
   const contentRef = useRef<HTMLDivElement>(null)
 
   const params = useParams()
-  // In sandbox mode pass empty strings so all workspace-scoped queries are disabled
-  const currentWorkflowId = isSandbox ? '' : (params.workflowId as string)
   const workspaceId = isSandbox ? '' : (params.workspaceId as string)
 
   const {
@@ -877,6 +875,8 @@ export const WorkflowBlock = memo(function WorkflowBlock({
     runPathStatus,
   } = useBlockVisual({ blockId: id, data, isPending, isSelected: selected })
 
+  const currentWorkflowId = isSandbox ? '' : (params.workflowId as string) || activeWorkflowId || ''
+
   const currentBlock = currentWorkflow.getBlockById(id)
 
   const { horizontalHandles, blockHeight, blockWidth, displayAdvancedMode, displayTriggerMode } =