[Applet]Supplementary add port check

Summary:
Supplementary to the previous commit.
2 More ports needs check. The issue is the same, maybe crash or
display warning, if the port does not exit when try to read description.

Reviewers: drosca, ngraham

Reviewed By: ngraham

Subscribers: plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D27086