Allow loading PostGIS Rasters from partially configured connections

Partially configured connection are those for which an hostname
or username or port etc. are not specified, relying on libpq defaults.

It was already fixed for geometries but rasters needed more love.
See #9037.

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

@@ -278,7 +278,13 @@ def info(self):
 	def gdalUri(self):
 		uri = self.database().uri()
 		schema = ( u'schema=%s' % self.schemaName() ) if self.schemaName() else ''
-		gdalUri = u'PG: dbname=%s host=%s user=%s password=%s port=%s mode=2 %s table=%s' % (uri.database(), uri.host(), uri.username(), uri.password(), uri.port(), schema, self.name)
+		dbname = ( u'dbname=%s' % uri.database() ) if uri.database() else ''
+		host = ( u'host=%s' % uri.host() ) if uri.host() else ''
+		user = ( u'user=%s' % uri.username() ) if uri.username() else ''
+		passw = ( u'password=%s' % uri.password() ) if uri.password() else ''
+		port = ( u'port=%s' % uri.port() ) if uri.port() else ''
+		gdalUri = u'PG: %s %s %s %s %s mode=2 %s table=%s' % \
+		  (dbname, host, user, passw, port, schema, self.name)
 		return gdalUri
 
 	def mimeUri(self):