fix fann_train_on_file and fann_cascadetrain_on_file to set at least …

…ann->errno_f if reading training data from file failed

examples/steepness_train.c

@@ -29,6 +29,11 @@ void train_on_steepness_file(struct fann *ann, char *filename,
 	unsigned int i;
 
 	struct fann_train_data *data = fann_read_train_from_file(filename);
+	if(data == NULL)
+	{
+		ann->errno_f = FANN_E_CANT_READ_TD;
+		return;
+	}
 
 	if(epochs_between_reports)
 	{

src/fann_cascade.c

@@ -134,6 +134,7 @@ FANN_EXTERNAL void FANN_API fann_cascadetrain_on_file(struct fann *ann, const ch
 
 	if(data == NULL)
 	{
+		ann->errno_f = FANN_E_CANT_READ_TD;
 		return;
 	}
 	fann_cascadetrain_on_data(ann, data, max_neurons, neurons_between_reports, desired_error);

src/fann_train_data.c

@@ -306,6 +306,7 @@ FANN_EXTERNAL void FANN_API fann_train_on_file(struct fann *ann, const char *fil
 
 	if(data == NULL)
 	{
+		ann->errno_f = FANN_E_CANT_READ_TD;
 		return;
 	}
 	fann_train_on_data(ann, data, max_epochs, epochs_between_reports, desired_error);