BF: the loading of sound in prefs was crashing dlg if invalid backend

because the wrong error type was being caught

psychopy/app/preferencesDlg.py

@@ -384,7 +384,7 @@ def __init__(self, parent, name, value, spec):
                         for thisDevName in devs:
                             if thisDevName not in options:
                                 options.append(thisDevName)
-                except DependencyError:
+                except ValueError:
                     pass
             else:
                 options = spec.replace("option(", "").replace("'", "")