Incorrect 1-4 vdW energies differences with OpenMM
Using the README example:

```python
In [32]: get_summary_data(out, combine_nonbonded_forces=True)
Out[32]:
             Bond      Angle   Torsion  Nonbonded       vdW  Electrostatics  RBTorsion
OpenMM   0.153073  37.844839  4.352785 -16.943223       NaN             NaN        NaN
Amber    0.151879  37.843025  4.352615        NaN  0.663164      -17.604598        NaN
GROMACS  0.153099  37.844906  4.352784        NaN  0.659480      -17.608341        0.0
LAMMPS   0.157495  37.844841  4.352785        NaN  0.655790      -17.617824        NaN

In [33]: get_summary_data(out, combine_nonbonded_forces=False)
Out[33]:
             Bond      Angle   Torsion  Electrostatics       vdW  RBTorsion
OpenMM   0.153073  37.844839  4.352785      -17.600324  1.316730        NaN
Amber    0.151879  37.843025  4.352615      -17.604598  0.663164        NaN
GROMACS  0.153099  37.844906  4.352784      -17.608341  0.659480        0.0
LAMMPS   0.157495  37.844841  4.352785      -17.617824  0.655790        NaN

In [34]: get_openmm_energies(out, combine_nonbonded_forces=False, detailed=True)
Out[34]: EnergyReport(energies={'vdW': <Quantity(-0.00252833093, 'kilojoule / mole')>, 'Electrostatics': <Quantity(20.0885625, 'kilojoule / mole')>, 'vdW 1-4': <Quantity(1.31925812, 'kilojoule / mole')>, 'Electrostatics 1-4': <Quantity(-37.6888862, 'kilojoule / mole')>, 'Torsion': <Quantity(4.35278514, 'kilojoule / mole')>, 'Angle': <Quantity(37.8448388, 'kilojoule / mole')>, 'Bond': <Quantity(0.153072926, 'kilojoule / mole')>})
```

The error appears to be isolated to OpenMM, using `combine_nonbonded_forces=False`, and likely results from errors in the 1-4 vdW force.
diff --git a/openff/interchange/interop/openmm/_nonbonded.py b/openff/interchange/interop/openmm/_nonbonded.py
index 7b15a107..604511a0 100644
--- a/openff/interchange/interop/openmm/_nonbonded.py
+++ b/openff/interchange/interop/openmm/_nonbonded.py
@@ -956,7 +956,7 @@ def _get_14_scaling_factors(data: _DATA_DICT) -> tuple[float, float]:
     else:
         coul_14 = 1.0
 
-    if data.get("vdw_handler", None) is not None:
+    if data.get("vdw_collection", None) is not None:
         vdw_14 = data["vdw_collection"].scale_14  # type: ignore[union-attr]
     else:
         vdw_14 = 1.0
['openff/interchange/interop/openmm/_nonbonded.py']