I was looking at the function reference for wp_dropdown_categories as I am trying to use it for part of my theme.
The parameter "hide_if_empty" says that 0/false will hide the dropdown if it is empty, and 1/true will show it, and that the default is 0/false. These documented values seem counter intuitive to the name.
It is true that the parameter is set to false by default. However, false shows it if it is empty, and true hides it (if empty_. It looks like the documentation has a typo in that these values are mixed up. The actual values fit in with the parameter name of "hide_if_empty".
I couldn't find anywhere else to report this, so I apologize if this is in the wrong section.