Fix (unreported) 'Duplicate Particle System' operator not ensuring

unique name

This was leading to equally named particle systems, causing problems
later on.
Spotted while looking into T67958.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D5632

source/blender/editors/physics/particle_object.c

@@ -1140,6 +1140,7 @@ static bool copy_particle_systems_to_object(const bContext *C,
 
     /* append to the object */
     BLI_addtail(&ob_to->particlesystem, psys);
+    psys_unique_name(ob_to, psys, psys->name);
 
     /* add a particle system modifier for each system */
     md = modifier_new(eModifierType_ParticleSystem);