Sample data: Fix plot without data.

View/sample_data_tab.py

@@ -776,6 +776,9 @@ class SampleDataTab(QWidget):
         self.combobox_acoustic_data.showPopup()
 
     def fill_comboboxes_and_plot_transect(self):
+        if len(stg.acoustic_data) == 0:
+            return
+
         self.combobox_acoustic_data.clear()
         for n, m in enumerate(stg.noise_method):
             if stg.noise_method[n] == 0: