Elide redundant 'pass' before 'raise PrimitiveFinished'

kernel/modelverse_jit/tree_ir.py

@@ -237,7 +237,8 @@ class ReturnInstruction(VoidInstruction):
 
     def generate_python_def(self, code_generator):
         """Generates Python code for this instruction."""
-        self.value.generate_python_def(code_generator)
+        if self.value.has_definition():
+            self.value.generate_python_def(code_generator)
         code_generator.append_line(
             'raise PrimitiveFinished(' +
             self.value.generate_python_use(code_generator) +