Octave subsref warnings: warning: 'uint64 matrix' object indexed with empty index list

[KrisThielemans]

#96 reinstated the subsref functions in Swigref.m. However, when running the test-suite with recent Octave, it generates lots of warnings like

warning: 'uint64 matrix' object indexed with empty index list
 warning: called from
  subsref at line 29 column 28

an example is generated at

swig/Examples/test-suite/matlab/default_args_runme.m

Line 18 in cd3f6c5

f = default_args.Foo();

This turns out to come from the following line in SwigRef.m (generated here)

[varargout{1}] = builtin('subsref',self,substruct('.',s.subs,'()',{}));

It is caused by the empty cell-array for (). The warning can be reproduced as follows

a.x=1;
subsref(a,substruct('.','x','()',{}))

This does returns 1 but with the same warning (but is silent in MATLAB).

The simple solution seems to use

[varargout{1}] = builtin('subsref',self,substruct('.',s.subs));

which has the desired effect