Sleep threads that have no taskroot anymore

kernel/modelverse_kernel/main.py

@@ -102,6 +102,7 @@ class ModelverseKernel(object):
     def execute_rule(self, taskname):
         task_root, =    yield [("RD", [self.root, taskname])]
         if task_root is None:
+            yield [("SLEEP", [0.01, False])]
             yield None
         else:
             task_frame, = yield [("RD", [task_root, "frame"])]
@@ -128,7 +129,6 @@ class ModelverseKernel(object):
                 elif inst_v is None:
                     raise Exception("%s: error understanding command (%s, %s)" % (self.debug_info[taskname], inst_v, self.phase_v))
                 else:
-                    #print("%-30s(%s) -- %s" % (inst_v["value"], self.phase_v, taskname))
                     gen = self.get_inst_phase_generator(inst_v, self.phase_v, task_root)
             elif inst_v is None:
                 raise Exception("%s: error understanding command (%s, %s)" % (self.debug_info[taskname], inst_v, self.phase_v))