fix: relax condition so that empty strings will also be filtered out

when the admin interface saves back a blank TextField, it saves it as
an empty string.

benefits/core/context_processors.py

@@ -15,7 +15,7 @@ def unique_values(original_list):
 def _agency_context(agency):
     return {
         "eligibility_index_url": agency.eligibility_index_url,
-        "help_templates": unique_values([v.help_template for v in agency.active_verifiers if v.help_template is not None]),
+        "help_templates": unique_values([v.help_template for v in agency.active_verifiers if v.help_template]),
         "info_url": agency.info_url,
         "long_name": agency.long_name,
         "phone": agency.phone,