Summary: Fix catching polymorphic type ‘class svn::ClientException’ by value [-Wcatch-value=] on GCC

Reviewers: #kdevelop, aaronpuchert

Reviewed By: #kdevelop, aaronpuchert

Subscribers: aaronpuchert, kdevelop-devel

Tags: #kdevelop

Differential Revision: https://phabricator.kde.org/D14678