fix: skip output node in FX graph cleanup to fix erase_node crash (Granite4 GPTQ)

Signed-off-by: gillesturpin <turpingilles@orange.fr>

Author: Yatimai

src/llmcompressor/pipelines/sequential/transformers_helpers.py

@@ -1478,9 +1478,28 @@ def to_meta(value):
                     to_delete = collections.OrderedDict()
                     while to_visit:
                         n = to_visit.pop(0)
+                        # Never mark the output node for deletion — instead
+                        # we will strip references to deleted nodes from it.
+                        if n.op == "output":
+                            continue
                         to_delete[n] = None
                         to_visit += list(n.users.keys())
 
+                    # Remove references to dead nodes from the output node
+                    for out_node in reversed(self.graph.nodes):
+                        if out_node.op == "output":
+
+                            def _strip(a):
+                                if isinstance(a, torch.fx.Node) and a in to_delete:
+                                    return None
+                                return a
+
+                            new_args = torch.fx.node.map_aggregate(
+                                out_node.args, _strip
+                            )
+                            out_node.args = new_args
+                            break
+
                     for user in reversed(to_delete.keys()):
                         self.graph.erase_node(user)