Bug in MATLAB function geodreckon

There's a bug in the MATLAB function geodreckon in calculating the area
when the distance argument is empty. The following patch fixes this.
This will be included in the next release of GeographicLib

diff --git a/matlab/geographiclib/geodreckon.m b/matlab/geographiclib/geodreckon.m
index 258e0e8..7751e7b 100644
--- a/matlab/geographiclib/geodreckon.m
+++ b/matlab/geographiclib/geodreckon.m
@@ -248,11 +248,14 @@ function [lat2, lon2, azi2, S12, m12, M12, M21, a12_s12] = geodreckon ...
                    ssig12 .* (csig1 .* ssig12 ./ (1 + csig12) + ssig1), ...
                    csig12 <= 0);
     calp12 = salp0.^2 + calp0.^2 .* csig1 .* csig2;
-    % Enlarge salp1, calp1 is case lat1 is an array and azi1 is a scalar
-    s = zeros(size(salp0)); salp1 = salp1 + s; calp1 = calp1 + s;
-    s = calp0 == 0 | salp0 == 0;
-    salp12(s) = salp2(s) .* calp1(s) - calp2(s) .* salp1(s);
-    calp12(s) = calp2(s) .* calp1(s) + salp2(s) .* salp1(s);
+    % Deal with geodreckon(10, 0, [], 0) which has calp2 = []
+    if length(Z) > 0
+      % Enlarge salp1, calp1 is case lat1 is an array and azi1 is a scalar
+      s = zeros(size(salp0)); salp1 = salp1 + s; calp1 = calp1 + s;
+      s = calp0 == 0 | salp0 == 0;
+      salp12(s) = salp2(s) .* calp1(s) - calp2(s) .* salp1(s);
+      calp12(s) = calp2(s) .* calp1(s) + salp2(s) .* salp1(s);
+    end
     if e2 ~= 0
       c2 = (a^2 + b^2 * eatanhe(1, e2) / e2) / 2;
     else