Properly deal with empty cache/directory in WFS provider, server and globe plugin

Fixes #15111

Author: rouault

src/plugins/globe/globe_plugin.cpp

@@ -342,7 +342,9 @@ void GlobePlugin::run()
   }
   else
   {
-    QString cacheDirectory = settings.value( "cache/directory", QgsApplication::qgisSettingsDirPath() + "cache" ).toString();
+    QString cacheDirectory = settings.value( "cache/directory" ).toString();
+    if ( cacheDirectory.isEmpty() )
+      cacheDirectory = QgsApplication::qgisSettingsDirPath() + "cache";
     osgEarth::Drivers::FileSystemCacheOptions cacheOptions;
     cacheOptions.rootPath() = cacheDirectory.toStdString();
 

src/providers/wfs/qgswfsutils.cpp

@@ -37,7 +37,9 @@ int QgsWFSUtils::gmCounter = 0;
 QString QgsWFSUtils::getBaseCacheDirectory( bool createIfNotExisting )
 {
   QSettings settings;
-  QString cacheDirectory = settings.value( "cache/directory", QgsApplication::qgisSettingsDirPath() + "cache" ).toString();
+  QString cacheDirectory = settings.value( "cache/directory" ).toString();
+  if ( cacheDirectory.isEmpty() )
+    cacheDirectory = QgsApplication::qgisSettingsDirPath() + "cache";
   if ( createIfNotExisting )
   {
     QMutexLocker locker( &gmMutex );

src/server/qgsserver.cpp

@@ -112,7 +112,9 @@ void QgsServer::setupNetworkAccessManager()
   QSettings settings;
   QgsNetworkAccessManager *nam = QgsNetworkAccessManager::instance();
   QNetworkDiskCache *cache = new QNetworkDiskCache( nullptr );
-  QString cacheDirectory = settings.value( "cache/directory", QgsApplication::qgisSettingsDirPath() + "cache" ).toString();
+  QString cacheDirectory = settings.value( "cache/directory" ).toString();
+  if ( cacheDirectory.isEmpty() )
+    cacheDirectory = QgsApplication::qgisSettingsDirPath() + "cache";
   qint64 cacheSize = settings.value( "cache/size", 50 * 1024 * 1024 ).toULongLong();
   QgsMessageLog::logMessage( QString( "setCacheDirectory: %1" ).arg( cacheDirectory ), "Server", QgsMessageLog::INFO );
   QgsMessageLog::logMessage( QString( "setMaximumCacheSize: %1" ).arg( cacheSize ), "Server", QgsMessageLog::INFO );