Fix 'label' undefined errors for sequential agents (#3585)

Fix 'label' undefined errors

Commit adds some optional chaining around 2 reads of 'label'
property.

Author: px-amaac

packages/server/src/utils/buildAgentGraph.ts

@@ -325,7 +325,7 @@ export const buildAgentGraph = async (
                                 // Send loading next agent indicator
                                 if (reasoning.next && reasoning.next !== 'FINISH' && reasoning.next !== 'END') {
                                     if (sseStreamer) {
-                                        sseStreamer.streamNextAgentEvent(chatId, mapNameToLabel[reasoning.next].label || reasoning.next)
+                                        sseStreamer.streamNextAgentEvent(chatId, mapNameToLabel[reasoning.next]?.label || reasoning.next)
                                     }
                                 }
                             }

packages/server/src/utils/buildChatflow.ts

@@ -218,7 +218,7 @@ export const utilBuildChatflow = async (req: Request, isInternal: boolean = fals
 
         /*** Get session ID ***/
         const memoryNode = findMemoryNode(nodes, edges)
-        const memoryType = memoryNode?.data.label
+        const memoryType = memoryNode?.data?.label
         let sessionId = getMemorySessionId(memoryNode, incomingInput, chatId, isInternal)
 
         /*** Get Ending Node with Directed Graph  ***/