fix null

Author: joaquim-verges

apps/playground-web/src/app/ai/api/chat.ts

@@ -22,7 +22,7 @@ export async function promptNebula(params: {
     body.context = {
       chain_ids: params.context.chainIds?.map(Number) || [],
       session_id: params.context.sessionId ?? undefined,
-      from: params.context.walletAddress,
+      from: params.context.walletAddress ?? undefined,
       auto_execute_transactions:
         params.context.autoExecuteTransactions || false,
     };