Handle CondFunc exception when resolving attributes

[Nuullll]

Description

• Handle potential AttributeError on getattr. This happens when orig_func string refers to a non-existent object.

For example, I attempted to hijack sd-webui-controlnet annotator.anime_face_segment.AnimeFaceSegment.__init__ in my extension. However, annotator.anime_face_segment is only available starting from ControlNet >= 1.1.420.

Screenshots/videos:

# Example usage
CondFunc('annotator.anime_face_segment.AnimeFaceSegment.__init__', ..., ...)
foo()

Before this change, an uncaught exception may be thrown at CondFunc instantiation, and foo() will not be executed unless we wrap every CondFunc with a try-except block, which is inconvenient.

      File "D:\stable-diffusion-webui\modules\sd_hijack_utils.py", line 15, in __new__
        resolved_obj = getattr(resolved_obj, attr_name)
    AttributeError: module 'annotator' has no attribute 'anime_face_segment'

After this change, a warning will be printed indicating this CondFunc didn't take effect:

Warning: Failed to resolve annotator.anime_face_segment.AnimeFaceSegment.__init__ for CondFunc hijack

Checklist:

• I have read contributing wiki page
• I have performed a self-review of my own code
• My code follows the style guidelines
• My code passes tests