Block in matfaust the kind of Faust indexing that create empty Faust and fix...

Block in matfaust the kind of Faust indexing that create empty Faust and fix by the way bug of issue #30.

wrapper/matlab/+matfaust/@Faust/Faust.m

@@ -1054,8 +1054,10 @@ classdef Faust
 						error(' Subscript indices must be integers >= 1.')
 					elseif(any(ind_list > size(F,i)))
 						error(' Index exceeds Faust dimensions.')
+					elseif(size(ind_list,2) == 0)
+						error(' Cannot create empty Faust')
 					end
-					% check if indices in range are indexing_by_slice
+					% check if indices in range are contiguous and not negative step
 					sl_sz = size(ind_list,2);
 					if(sl_sz >= 2)
 						% TODO: couldn't be without a loop by verifiying two shifted views of array ?