QuantumCircuit.decompose raises an error with a conditional U gate for Qiskit 1.3.0rc2 and the main branch

[t-imamichi]

Environment

• Qiskit version: 1.3.0rc2, main
• Python version: 3.12.7
• Operating system: macOS 15.1.1

What is happening?

A circuit with a conditional gate raises an error when decompose is invoked. It does not happen for 1.2.4

How can we reproduce the issue?

from qiskit import QuantumCircuit, __version__

qc = QuantumCircuit(1, 1)
qc.u(0, 0, 0, 0).c_if(0, 0)

print(__version__)
print(qc)
print(qc.decompose())

# qiskit 1.2.4
1.2.4
     ┌──────────┐
  q: ┤ U(0,0,0) ├
     └────╥─────┘
     ┌────╨────┐
c: 1/╡ c_0=0x0 ╞═
     └─────────┘
     ┌──────────┐
  q: ┤ U(0,0,0) ├
     └────╥─────┘
     ┌────╨────┐
c: 1/╡ c_0=0x0 ╞═
     └─────────┘

# 1.3.0rc2 and main branch
1.3.0rc2
     ┌──────────┐
  q: ┤ U(0,0,0) ├
     └────╥─────┘
     ┌────╨────┐
c: 1/╡ c_0=0x0 ╞═
     └─────────┘
Traceback (most recent call last):
  File "/Users/ima/tasks/4_2024/qiskit/terra/tmp/cond.py", line 8, in <module>
    print(qc.decompose())
          ^^^^^^^^^^^^^^
  File "/Users/ima/envs/q130/lib/python3.12/site-packages/qiskit/circuit/quantumcircuit.py", line 3288, in decompose
    dag = pass_.run(dag)
          ^^^^^^^^^^^^^^
  File "/Users/ima/envs/q130/lib/python3.12/site-packages/qiskit/transpiler/passes/basis/decompose.py", line 72, in run
    node_as_dag = _node_to_dag(node)
                  ^^^^^^^^^^^^^^^^^^
  File "/Users/ima/envs/q130/lib/python3.12/site-packages/qiskit/transpiler/passes/basis/decompose.py", line 130, in _node_to_dag
    dag.apply_operation_back(node.op, node.qargs, node.cargs)
qiskit.dagcircuit.exceptions.DAGCircuitError: 'invalid clbits in condition for u'

What should happen?

No error should be raised as same as 1.2.4

Any suggestions?

The following procedure, which exists in stable/1.2, is perhaps necessary to handle UGate.c_if in _apply_op_node_back?

qiskit/qiskit/dagcircuit/dagcircuit.py

Lines 722 to 726 in cd26d49

	def _apply_op_node_back(self, node: DAGOpNode, *, check: bool = False):
	additional = ()
	if _may_have_additional_wires(node):
	# This is the slow path; most of the time, this won't happen.
	additional = set(_additional_wires(node.op)).difference(node.cargs)