[processing] fixed adding raster layer to project

fixes #13791

Author: volaya

python/plugins/processing/gui/Postprocessing.py

@@ -59,7 +59,7 @@ def handleAlgorithmResults(alg, progress=None, showResults=True):
             continue
         if isinstance(out, (OutputRaster, OutputVector, OutputTable)):
             try:
-                if out.layer is not None:
+                if hasattr(out, "layer") and out.layer is not None:
                     out.layer.setLayerName(out.description)
                     QgsMapLayerRegistry.instance().addMapLayers([out.layer])
                 else: