Fix alert dialog icon

Previously, failing to call setIcon() would result in a blank icon
rather than hiding the icon. Also, calling setIcon(icon) followed by
setIcon(null) could be a no-op depending on whether the alert had
already been constructed.

Change-Id: I65a96a4e89b9eac1123cbbf5d57e7e366e7b4d4e
1 file changed