Confusing default text in the "Set Stack Adjustment" dialog

[xusheng6]

In the set stack adjustment dialog, when the current address does not have a stack adjustment, the dialog shows the last value from the history ui/stackAdjustSizeHistory. This can be confusing since it can be understood as the current stack adjustment is the value shown, e.g., in the below screenshot, 0x4.

We should probably show it as 0x0 if the stack adjustment is indeed 0x0