Fix a bug in the unary lowering code

kernel/modelverse_jit/cfg_to_tree.py

@@ -813,7 +813,7 @@ class LoweringState(object):
 
     def lower_unary(self, value):
         """Lowers a 'unary' value."""
-        operand, = self.use_definition(value.operand)
+        operand = self.use_definition(value.operand)
         return tree_ir.UnaryInstruction(value.operator, operand)
 
     def lower_direct_call(self, value):