Fix GCC warning
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