fix a fix missed in merge of fixes from devbr6 https://trac.osgeo.org/grass/changeset/42003

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@56925 15284696-431f-4ddb-bdfa-cd5b030d7da7

scripts/v.krige/v.krige.py

@@ -187,7 +187,7 @@ class Controller:
         if isblock is True:
             predictor = 'x+y'
         else:
-            predictor = 1
+            predictor = '1'
         Formula = robjects.Formula(column + "~" + predictor)
         #print Formula
         return Formula