fix(UImageViewer): zIndex should be bigger then in an ancestor dialog
Initialize viewer in the next tick to take a bigger value $zIndex() than in some ancestor dialog.
zIndex of dialog is usually calculated in the mounted
hook too but the mounted
hook is called in the child first.
So, we should let the parent mounted
happen firstly
Described in the LDOC-3178
Edited by Mazur Volodymyr