[BUG] qml.equal does not work with qml.GlobalPhase

[KetpuntoG]

Expected behavior

qml.equal(qml.PauliX(0)@qml.GlobalPhase(np.pi), qml.PauliX(0)@qml.GlobalPhase(np.pi))

This should be true

Actual behavior

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
[<ipython-input-16-74827f3d67e3>](https://hmoo5kikp7-496ff2e9c6d22116-0-colab.googleusercontent.com/outputframe.html?vrz=colab_20240408-060136_RC00_622797729#) in <cell line: 1>()
----> 1 qml.equal(qml.PauliX(0)@qml.GlobalPhase(np.pi), qml.PauliX(0)@qml.GlobalPhase(np.pi))

4 frames
[/usr/local/lib/python3.10/dist-packages/pennylane/ops/op_math/prod.py](https://hmoo5kikp7-496ff2e9c6d22116-0-colab.googleusercontent.com/outputframe.html?vrz=colab_20240408-060136_RC00_622797729#) in _swappable_ops(op1, op2, wire_map)
    545     wires2 = set(wires2)
    546     # compare strings of wire labels so that we can compare arbitrary wire labels like 0 and "a"
--> 547     return False if wires1 & wires2 else str(wires1.pop()) > str(wires2.pop())
    548 
    549 

KeyError: 'pop from an empty set'

Additional information

if I specify the wires in GlobalPhase, it works

Source code

No response

Tracebacks

No response

System information

Name: PennyLane
Version: 0.36.0.dev0
Summary: PennyLane is a cross-platform Python library for quantum computing, quantum machine learning, and quantum chemistry. Train a quantum computer the same way as a neural network.
Home-page: https://github.com/PennyLaneAI/pennylane
Author: 
Author-email: 
License: Apache License 2.0
Location: /usr/local/lib/python3.10/dist-packages
Requires: appdirs, autograd, autoray, cachetools, networkx, numpy, pennylane-lightning, requests, rustworkx, scipy, semantic-version, toml, typing-extensions
Required-by: PennyLane_Lightning

Platform info:           Linux-6.1.58+-x86_64-with-glibc2.35
Python version:          3.10.12
Numpy version:           1.25.2
Scipy version:           1.11.4
Installed devices:
- lightning.qubit (PennyLane_Lightning-0.35.1)
- default.clifford (PennyLane-0.36.0.dev0)
- default.gaussian (PennyLane-0.36.0.dev0)
- default.mixed (PennyLane-0.36.0.dev0)
- default.qubit (PennyLane-0.36.0.dev0)
- default.qubit.autograd (PennyLane-0.36.0.dev0)
- default.qubit.jax (PennyLane-0.36.0.dev0)
- default.qubit.legacy (PennyLane-0.36.0.dev0)
- default.qubit.tf (PennyLane-0.36.0.dev0)
- default.qubit.torch (PennyLane-0.36.0.dev0)
- default.qutrit (PennyLane-0.36.0.dev0)
- null.qubit (PennyLane-0.36.0.dev0)

Existing GitHub issues

• I have searched existing GitHub issues to make sure the issue does not already exist.