[Bugfix] Fix NameError in OmniDiffusion init for Bagel/NextStep after GLM-Image merge

[lishunyang12]

Summary

• PR [Perf] GLM Image #920 (GLM-Image support) refactored the model-type dispatch in OmniDiffusion.__init__ but introduced a bug: the GLM-Image and single-architecture branches assign to a local pipeline_class variable, while lines 93-98 unconditionally read it. When Bagel or NextStep models hit their branches (which set od_config directly), pipeline_class is never defined, causing a NameError.
• Fix: make each branch self-contained — every branch sets od_config.model_class_name, tf_model_config, and calls update_multimodal_support() directly. No shared pipeline_class variable needed.

Test plan

• Verify Bagel model loads without crash: OmniDiffusion(model="ByteDance-Seed/BAGEL-7B-MoT")
• Verify GLM-Image still works: OmniDiffusion(model="THUDM/GLM-Image-1.0")
• Verify single-architecture fallback path still works

[lishunyang12]

Verified the bug and fix by simulating the dispatch logic in OmniDiffusion.__init__ :

--- BEFORE fix (main branch logic) ---
  Bagel       : FAIL: cannot access local variable 'pipeline_class' where it is not associated with a value
  NextStep    : FAIL: cannot access local variable 'pipeline_class' where it is not associated with a value
  GLM-Image   : OK
  Single-arch : OK

--- AFTER fix (PR #1563 logic) ---
  Bagel       : OK
  NextStep    : OK
  GLM-Image   : OK
  Single-arch : OK

Bagel/NextStep branches set od_config directly but fall through to lines 93-98 which read the never-defined pipeline_class → NameError. Making each branch self-contained fixes it cleanly.

[hsliuustc0106]

Verified the bug and fix by simulating the dispatch logic in OmniDiffusion.__init__ :

--- BEFORE fix (main branch logic) ---
  Bagel       : FAIL: cannot access local variable 'pipeline_class' where it is not associated with a value
  NextStep    : FAIL: cannot access local variable 'pipeline_class' where it is not associated with a value
  GLM-Image   : OK
  Single-arch : OK

--- AFTER fix (PR #1563 logic) ---
  Bagel       : OK
  NextStep    : OK
  GLM-Image   : OK
  Single-arch : OK

Bagel/NextStep branches set od_config directly but fall through to lines 93-98 which read the never-defined pipeline_class → NameError. Making each branch self-contained fixes it cleanly.

fix DCO

[Semmer2]

Hi, Shunyang, I thinke these three lines of code is common, which should not be deleted and added in former if-else code.