[Qt] Added error handling stubs

platform/qt/include/qquickmapboxgl.hpp

@@ -2,6 +2,7 @@
 #define QQUICKMAPBOXGL_H
 
 #include <QGeoCoordinate>
+#include <QGeoServiceProvider>
 #include <QGeoShape>
 #include <QQuickFramebufferObject>
 
@@ -11,10 +12,13 @@ class Q_DECL_EXPORT QQuickMapboxGL : public QQuickFramebufferObject
 {
     Q_OBJECT
 
+    Q_ENUMS(QGeoServiceProvider::Error)
     Q_PROPERTY(qreal minimumZoomLevel READ minimumZoomLevel WRITE setMinimumZoomLevel NOTIFY minimumZoomLevelChanged)
     Q_PROPERTY(qreal maximumZoomLevel READ maximumZoomLevel WRITE setMaximumZoomLevel NOTIFY maximumZoomLevelChanged)
     Q_PROPERTY(qreal zoomLevel READ zoomLevel WRITE setZoomLevel NOTIFY zoomLevelChanged)
     Q_PROPERTY(QGeoCoordinate center READ center WRITE setCenter NOTIFY centerChanged)
+    Q_PROPERTY(QGeoServiceProvider::Error error READ error NOTIFY errorChanged)
+    Q_PROPERTY(QString errorString READ errorString NOTIFY errorChanged)
     Q_PROPERTY(QGeoShape visibleRegion READ visibleRegion WRITE setVisibleRegion)
     Q_PROPERTY(bool copyrightsVisible READ copyrightsVisible WRITE setCopyrightsVisible NOTIFY copyrightsVisibleChanged)
     Q_PROPERTY(QColor color READ color WRITE setColor NOTIFY colorChanged)
@@ -38,6 +42,9 @@ public:
     void setCenter(const QGeoCoordinate &center);
     QGeoCoordinate center() const;
 
+    QGeoServiceProvider::Error error() const;
+    QString errorString() const;
+
     void setVisibleRegion(const QGeoShape &shape);
     QGeoShape visibleRegion() const;
 
@@ -62,6 +69,7 @@ signals:
     void centerChanged(const QGeoCoordinate &coordinate);
 
     // Compatibility with Map QML Type, but no-op.
+    void errorChanged();
     void copyrightLinkActivated(const QString &link);
     void copyrightsVisibleChanged(bool visible);
     void colorChanged(const QColor &color);

platform/qt/src/qquickmapboxgl.cpp

@@ -102,6 +102,15 @@ QGeoCoordinate QQuickMapboxGL::center() const
     return m_center;
 }
 
+QGeoServiceProvider::Error QQuickMapboxGL::error() const
+{
+    return QGeoServiceProvider::NoError;
+}
+
+QString QQuickMapboxGL::errorString() const
+{
+    return QString();
+}
 
 void QQuickMapboxGL::setVisibleRegion(const QGeoShape &shape)
 {