Fixed initialization of empty sub-options.

kiplot/optionable.py

@@ -21,6 +21,7 @@ class Optionable(object):
 
     def __init__(self):
         self._unkown_is_error = False
+        self._tree = {}
         super().__init__()
         if GS.global_output is not None and getattr(self, 'output', None):
             setattr(self, 'output', GS.global_output)

kiplot/out_base.py

@@ -42,6 +42,8 @@ class BaseOutput(RegOutput):
         if getattr(self, 'options', None) and isinstance(self.options, type):
             # No options, get the defaults
             self.options = self.options()
+            # Configure them using an empty tree
+            self.options.config()
 
     def run(self, output_dir, board):
         self.options.run(output_dir, board)