Inconsistent space in the definition of UNUSED

There is an inconsistent space in the definition of UNUSED in various parts of LALSuite, including just in LALSimulation, e.g., LALSimInspiralPNCoefficients.c and most other parts of LALSuite have

#define UNUSED __attribute__ ((unused))

while PhenomX files, e.g., LALSimIMRPhenomX_internals.h, but also a few other parts of LALSuite (mostly in LALSimulation) have

#define UNUSED __attribute__((unused))

This leads to compilation errors of the type given below if one tries to include files with more than one version of this definition in another file.

LALSimIMRPhenomXHM_inspiral.h:35:0: error: "UNUSED" redefined [-Werror]
 #define UNUSED __attribute__((unused))
 ^

Is there a preference or reason for having this be with or without the space?

@david-keitel said that he'd found the version without the space "recommended on most tutorial sites," though I see the version with the space in official GCC documentation. This inconsistency has come up in the in-progress implementation of IMRPhenomXP_NRTidalv2, so it will be good to have a recommendation soon. Thanks!