add missing variable

models/boneload.py

@@ -344,6 +344,7 @@ def create_loads(nodes, tris, total_force, target, method='T'):
     if method=='U':
         project = False
         methodtxt='Ad Hoc Uniform Traction Model'
+        normal_comp = None
     elif method=='T':
         project = True 
         normal_comp = False