grass.script: Fix missing passing of env parameter

The original change in PR OSGeo#3439 has None instead of env passed to the error function in the fatal function. This passes the env parameter.

python/grass/script/core.py

@@ -766,7 +766,7 @@ def fatal(msg, env=None):
     if raise_on_error:
         raise ScriptError(msg)
 
-    error(msg, env=None)
+    error(msg, env=env)
     sys.exit(1)