[processing] Fix error when creating tests and raster output

no longer exists

Fixes #16123

Author: nyalldawson

python/plugins/processing/gui/TestTools.py

@@ -263,6 +263,15 @@ def createTest(text):
                 return
 
             dataset = gdal.Open(token, GA_ReadOnly)
+            if dataset is None:
+                QMessageBox.warning(None,
+                                    tr('Error'),
+                                    tr('Seems some outputs are temporary '
+                                       'files. To create test you need to '
+                                       'redirect all algorithm outputs to '
+                                       'files'))
+                return
+
             dataArray = nan_to_num(dataset.ReadAsArray(0))
             strhash = hashlib.sha224(dataArray.data).hexdigest()