Fix the bug of checking loop limit

[tczpl]

When leaving the block, the counter of the current edge should decrease by 1.

For example: Executing 1-5-2-7-Terminal and 1-6-2-7-Terminal.

Before this commit: The visit_edges["2-7"] is 1 and 2.

After this commit: The visit_edges["2-7"] is 1 and 1, which is correct.