GtTaskStatistics: added safety check

Signed-off-by: Nicola Vigano <nicola.vigano@esrf.fr>

zUtil_DataStructures/GtTasksStatistics.m

@@ -31,6 +31,10 @@ classdef GtTasksStatistics < handle
         end
 
         function add_task_partial(self, name, partial_name, description)
+            if (~isfield(self.entries, name))
+                error('GtTasksStatistics:wrong_argument', ...
+                    'Task name "%s" does not exist!', name)
+            end
             self.entries.(name).partials.(partial_name) ...
                 = struct('description', description, 'timestamps', [], 'timer_tic', 0);
         end