How Do I Make A Cell Appear Empty When another Formula is in place?

I am using Excel to make usernames for an online system, but the providers of the names that need to go on the system don't always provide good quality text. As a result, in addition to using ampersands I have to put a Substitute function in order to remove spaces not only in between multi part names, but at the end of the names as well. This works well, but when it extends into empty cells (which have the formula in place) a small black dot dot appears on the left and then when we load the names on the system, these empty "dot" cells seem to try to come up as users. Is there any way of getting rid of this without having to delete the formula from the cell? (We have to input different groups and update them regularly, so want to avoid having to drag the formatting down everytime we do it)
THis is the formula I am using - =SUBSTITUTE(E5," ","")&"."&SUBSTITUTE(F5," ","")