Test the existence of the request context key before using it for URL

Closes #15046
(grafted from 5eae02e6c094d6741d615d1c4bd2333721eb92b7)

--HG--
branch : 7.0

trytond/trytond/url.py

@@ -27,7 +27,7 @@ class URLAccessor(object):
         context = Transaction().context
         if context:
             request = context.get('_request')
-            if request and request['is_secure']:
+            if request and request.get('is_secure'):
                 return True
         return bool(
             config.get('ssl', 'certificate')
@@ -38,7 +38,7 @@ class URLAccessor(object):
         context = Transaction().context
         if context:
             request = context.get('_request')
-            if request:
+            if request and 'http_host' in request:
                 return request['http_host']
         return HOSTNAME