Send to device: Use default save template when driver specific one is empty or unspecified

src/calibre/devices/usbms/device.py

@@ -805,7 +805,7 @@ class Device(DeviceConfig, DevicePlugin):
                     break
 
         settings = self.settings()
-        template = settings.save_template
+        template = self.save_template()
         use_subdirs = self.SUPPORTS_SUB_DIRS and settings.use_subdirs
 
         fname = sanitize(fname)

src/calibre/devices/usbms/deviceconfig.py

@@ -70,6 +70,14 @@ class DeviceConfig(object):
     def settings(cls):
         return cls._config().parse()
 
+    @classmethod
+    def save_template(cls):
+        st = cls.settings().save_template
+        if st:
+            return st
+        else:
+            return cls._default_save_template()
+
     @classmethod
     def customization_help(cls, gui=False):
         return cls.HELP_MESSAGE