Workflow search_spaces crashes when hardware value is a dict

While testing Gradio Workflows, the terminal repeatedly logs an AttributeError from `_has_zero_gpu` because `hw` is sometimes a dict instead of a string. Traceback excerpt: ```text File "/Users/abubakar/dev/gradio/gradio/workflow.py", line 679, in _has_zero_gpu return "zero" in hw.lower() ^^^^^^^^ AttributeError: 'dict' object has no attribute 'lower' search_spaces failed (kind=trending): 'dict' object has no attribute 'lower' search_spaces failed (kind=new): 'dict' object has no attribute 'lower' ``` Expected behavior: Workflow Space search should handle hardware values returned as dicts without repeatedly logging crashes.