Convert variable-sized signal to fixed

I have a custom block (block on the right) that takes a fixed size signal, but I would like to adjust the size of the input signal as needed. The subsystem that is present 10 times in the photo below outputs a number if it's input is 1 or an empty signal if it is zero. Then I make the 10 signals into 1 using a bus selector. However, the output signal of the bus selector is of variable-size. Is there any way to convert a variable sized signal to fixed?