Fix build with Qt 5.15

Differential Revision: https://phabricator.kde.org/D28173

src/assets/view/widgets/curves/bezier/beziersplineeditor.cpp

@@ -24,6 +24,7 @@
 
 #include <QMouseEvent>
 #include <QPainter>
+#include <QPainterPath>
 
 BezierSplineEditor::BezierSplineEditor(QWidget *parent)
     : AbstractCurveWidget(parent)

src/bin/abstractprojectitem.cpp

@@ -32,6 +32,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "jobs/thumbjob.hpp"
 
 #include <QPainter>
+#include <QPainterPath>
 #include <QVariant>
 #include <utility>
 AbstractProjectItem::AbstractProjectItem(PROJECTITEMTYPE type, QString id, const std::shared_ptr<ProjectItemModel> &model, bool isRoot)

src/titler/gradientwidget.cpp

@@ -23,6 +23,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #include <QLinearGradient>
 #include <QPainter>
+#include <QPainterPath>
 #include <QPixmap>
 #include <QtMath>