more robust type cast in I/O functions

utils/sample_combine.cpp

@@ -187,7 +187,7 @@ int main(int argc, char *argv[])
     {
         process<DSample>(outFileName, fileName, code);
     }
-    catch (bad_cast &e)
+    catch (Exceptions::Definition)
     {
         process<DMatSample>(outFileName, fileName, code);
     }

utils/sample_read.cpp

@@ -46,7 +46,7 @@ int main(int argc, char *argv[])
             Io::save(s, copy, File::Mode::write, name);
         }
     }
-    catch (bad_cast &e)
+    catch (Exceptions::Definition)
     {
         DSample s    = Io::load<DSample>(fileName);
         string  name = Io::getFirstName(fileName);