Update null-check function for aibitat runners (#3283)

server/utils/agents/aibitat/providers/anthropic.js

server/utils/agents/aibitat/providers/apipie.js

server/utils/agents/aibitat/providers/azure.js

server/utils/agents/aibitat/providers/bedrock.js

server/utils/agents/aibitat/providers/deepseek.js

server/utils/agents/aibitat/providers/fireworksai.js

server/utils/agents/aibitat/providers/genericOpenAi.js

server/utils/agents/aibitat/providers/groq.js

server/utils/agents/aibitat/providers/koboldcpp.js

server/utils/agents/aibitat/providers/litellm.js

server/utils/agents/aibitat/providers/lmstudio.js

server/utils/agents/aibitat/providers/localai.js

server/utils/agents/aibitat/providers/mistral.js

server/utils/agents/aibitat/providers/novita.js

server/utils/agents/aibitat/providers/nvidiaNim.js

server/utils/agents/aibitat/providers/ollama.js

server/utils/agents/aibitat/providers/openai.js

server/utils/agents/aibitat/providers/openrouter.js

server/utils/agents/aibitat/providers/perplexity.js

server/utils/agents/aibitat/providers/textgenwebui.js