Delete provider registry actively

Fixes a crash on exit

Author: m-kuhn

src/core/qgsapplication.cpp

@@ -595,6 +595,8 @@ void QgsApplication::initQgis()
 void QgsApplication::exitQgis()
 {
   delete QgsMapLayerRegistry::instance();
+
+  delete QgsProviderRegistry::instance();
 }
 
 QString QgsApplication::showSettings()

src/core/qgsproviderregistry.cpp

@@ -47,8 +47,8 @@ typedef QString protocolDrivers_t();
 
 QgsProviderRegistry *QgsProviderRegistry::instance( QString pluginPath )
 {
-  static QgsProviderRegistry mInstance( pluginPath );
-  return &mInstance;
+  static QgsProviderRegistry* sInstance( new QgsProviderRegistry( pluginPath ) );
+  return sInstance;
 } // QgsProviderRegistry::instance