Fix dfki-ric#366

Author: AlpenAalAlex

phobos/io/representation.py

@@ -1679,10 +1679,8 @@ def __init__(self, joint=None, multiplier=None, offset=None, **kwargs):
         super().__init__()
         self.joint = _singular(joint)
         assert self.joint is not None
-        self.multiplier = multiplier
-        assert self.multiplier is not None
-        self.offset = offset
-        assert self.offset is not None
+        self.multiplier = multiplier or 1
+        self.offset = offset or 0
         self.returns += ["joint", "multiplier", "offset"]
 
     def equivalent(self, other):