Fixed bug that crashed program when clicking Forecast->Chart
BUG: 400820
FIXED-IN: 5.0.3
Reviewers: KMyMoney, tbaumgart
Reviewed By: KMyMoney, tbaumgart
Subscribers: tbaumgart
Differential Revision: https://phabricator.kde.org/D17368
(cherry picked from commit 6ba86e8d02dc3dc7fc57b66097a5803c96c22571)