Fixed bug related to the initialization of the dseries and dates object (test...

Fixed bug related to the initialization of the dseries and dates object (test that the input argument is a string).

matlab/@dates/dates.m

@@ -62,7 +62,7 @@ function dd = dates(varargin) % --*-- Unitary tests --*--
 % You should have received a copy of the GNU General Public License
 % along with Dynare.  If not, see <http://www.gnu.org/licenses/>.
 
-if nargin>0 && isequal(varargin{1},'initialize')
+if nargin>0 && ischar(varargin{1}) && isequal(varargin{1},'initialize')
     dd = struct('ndat', 0, 'freq', NaN(0), 'time', NaN(0,2));
     dd = class(dd,'dates');
     assignin('base','emptydatesobject',dd);

matlab/@dseries/dseries.m

@@ -76,7 +76,7 @@ function ts = dseries(varargin) % --*-- Unitary tests --*--
 % You should have received a copy of the GNU General Public License
 % along with Dynare.  If not, see <http://www.gnu.org/licenses/>.
 
-if nargin>0 && isequal(varargin{1},'initialize')
+if nargin>0 && ischar(varargin{1}) && isequal(varargin{1},'initialize')
     ts = struct;
     ts.data  = [];
     ts.nobs  = 0;