avoid uninitialized data access

src/modify.cpp

@@ -80,6 +80,7 @@ Modify::Modify(LAMMPS *lmp) : Pointers(lmp)
 
   list_timeflag = nullptr;
 
+  restart_pbc_any = 0;
   nfix_restart_global = 0;
   id_restart_global = style_restart_global = nullptr;
   state_restart_global = nullptr;