Fixed bug in horizontal concatenation of empty quantities

+quantity/Discrete.m

@@ -494,7 +494,13 @@ classdef  (InferiorClasses = {?quantity.Symbolic, ?quantity.Operator}) Discrete
 					% if there are only empty entries, nothing can be
 					% concatenated, so a new empty object is initialized.
 					s = cellfun(@(o) size(o), objCell, 'UniformOutput', false);
-					S = sum(cat(3, s{:}), 3);
+					if dim == 1
+						S = sum(cat(3, s{:}), 3);
+					elseif dim == 2
+						S = s{1};
+					else
+						error('Not implemented')
+					end
 					c = quantity.Discrete.empty(S);
 					return
 				else

+unittests/+quantity/testDiscrete.m

@@ -77,6 +77,13 @@ testCase.verifyTrue(all(size(AC) == [4, 1]));
 A0s = [A, zeros(2,3)];
 testCase.verifyTrue(all(all(all(A0s(:, 2:end).on() == 0))))
 
+O = quantity.Discrete.empty([5, 0]);
+O_horz = [O, O];
+O_vert = [O; O];
+
+testCase.verifyEqual(size(O_horz, 1), 5);
+testCase.verifyEqual(size(O_vert, 1), 10);
+
 end
 
 function testExp(testCase)