[dbmanager] Fix error when connecting to postgis db

Fixes #19240

Author: nyalldawson

python/plugins/db_manager/db_plugins/postgis/plugin.py

@@ -85,7 +85,10 @@ def connect(self, parent=None):
         service, host, port, database, username, password, authcfg = [settings.value(x, "", type=str) for x in settingsList]
 
         useEstimatedMetadata = settings.value("estimatedMetadata", False, type=bool)
-        sslmode = settings.value("sslmode", QgsDataSourceUri.SslPrefer, type=int)
+        try:
+            sslmode = settings.value("sslmode", QgsDataSourceUri.SslPrefer, type=int)
+        except TypeError:
+            sslmode = QgsDataSourceUri.SslPrefer
 
         settings.endGroup()