Listing 8.13 - Incorrect Implementation

[ITHelpDec]

Most of this has been addressed in an earlier issue, so thank you to @dragon-dreamer and @xxrlzzz.

• Listing 8.13 contains a mistake (on github and in the book as well) #5

As it stands, an incomplete join_threads will result in a runtime error, and functionally we need to ensure an else statement is included should update_source not return true.

Our block_start iterator is also unused, so maybe this was a throwback to earlier examples where block_start and block_end were passed recursively?

Good catch, guys / dolls.