Fix syntax errors and ensure CPU fallback in model_management; make SageAttention patch robust

app.py

@@ -22,16 +22,17 @@ def apply_sage_attention_patch():
     try:
         from comfy import model_management
         import sageattention
-        
         print("--- [Runtime Patch] sageattention package found. Applying patch... ---")
-        model_management.sage_attention_enabled = lambda: True
-        model_management.pytorch_attention_enabled = lambda: False
-        
+        # Safely set flags if they exist; on CPU-only setups model_management may be limited.
+        if hasattr(model_management, "sage_attention_enabled"):
+            model_management.sage_attention_enabled = lambda: True
+        if hasattr(model_management, "pytorch_attention_enabled"):
+            model_management.pytorch_attention_enabled = lambda: False
         SAGE_PATCH_APPLIED = True
         return "✅ Successfully enabled SageAttention."
-    except ImportError:
+    except Exception as e:
         SAGE_PATCH_APPLIED = False
-        msg = "--- [Runtime Patch] ⚠️ sageattention package not found. Continuing with default attention. ---"
+        msg = f"--- [Runtime Patch] ⚠️ SageAttention patch could not be applied: {e} ---"
         print(msg)
         return msg
     except Exception as e: