[Qt] Prevent double deletion of progress dialog
[Qt] Prevent double deletion of progress dialog

When `showProgress()` is passed a `100` int value, the dialog is deleted
. If the function is passed a `100` int value a second time in the same
scope, like what happens at the end of `RecalculateZPIVSpent()` and
`RecalculateZPIVSupply()`, it results in a segfault.

This change standardizes the process by first initializing the progress
dialog with a `0` value, updating to a maximum of a `99` value inside
the loop, and finally closing with a `100` value after the loop has
completed.

npccoin/npccoin,Mrs-X/PIVX,PIVX-Project/PIVX,Darknet-Crypto/Darknet,Darknet-Crypto/Darknet,benzmuircroft/REWIRE.io,Darknet-Crypto/Darknet,npccoin/npccoin,Mrs-X/PIVX,npccoin/npccoin,Mrs-X/Darknet,Mrs-X/PIVX,benzmuircroft/REWIRE.io,PIVX-Project/PIVX,Darknet-Crypto/Darknet,PIVX-Project/PIVX,PIVX-Project/PIVX,Darknet-Crypto/Darknet,Mrs-X/PIVX,Mrs-X/Darknet,PIVX-Project/PIVX,npccoin/npccoin,Mrs-X/PIVX,Darknet-Crypto/Darknet,Mrs-X/Darknet,Mrs-X/Darknet,benzmuircroft/REWIRE.io,benzmuircroft/REWIRE.io,npccoin/npccoin,Mrs-X/Darknet,PIVX-Project/PIVX,npccoin/npccoin,benzmuircroft/REWIRE.io,Mrs-X/Darknet,PIVX-Project/PIVX,PIVX-Project/PIVX,PIVX-Project/PIVX,benzmuircroft/REWIRE.io,Mrs-X/PIVX