Warning: Trying to access array offset on null in GetFieldDisplayForm::execute()
## **Problem/Motivation**
When using the AI Assistant / AI Agents field tools, a PHP warning is triggered in GetFieldDisplayForm::execute().
The code appears to assume that field display/form configuration data is always available, but in this case the value is NULL and the plugin attempts to access it as an array.
This happens in:
modules/contrib/ai_agents/src/Plugin/AiFunctionCall/GetFieldDisplayForm.php line 190
## Error
Warning: Trying to access array offset on null in Drupal\\ai_agents\\Plugin\\AiFunctionCall\\GetFieldDisplayForm-\>execute() (line 190 of modules/contrib/ai_agents/src/Plugin/AiFunctionCall/GetFieldDisplayForm.php).
Drupal\\ai_agents\\Plugin\\AiFunctionCall\\GetFieldDisplayForm-\>execute() Drupal\\ai_agents\\PluginBase\\AiAgentEntityWrapper-\>executeTool() Drupal\\ai_agents\\PluginBase\\AiAgentEntityWrapper-\>determineSolvability() Drupal\\ai_agents\\Plugin\\AiFunctionCall\\AiAgentWrapper-\>execute() Drupal\\ai_assistant_api\\Service\\AgentRunner-\>runAsAgent() Drupal\\ai_assistant_api\\AiAssistantApiRunner-\>process() Drupal\\ai_chatbot\\Controller\\DeepChatApi-\>api()
## Steps to reproduce
1. Install/configure Drupal with the AI module, AI Agents, AI Assistant API and AI Chatbot.
2. Use the AI Assistant / chatbot with an agent that calls the field display/form tool.
3. Ask it to create or edit a page
4. Check watchdog/PHP logs.
Actual result: A PHP warning is logged: "Trying to access array offset on null" in GetFieldDisplayForm.php line 190.
issue