Enable some Lint cops to prevent warnings (#951)

Parity with ActiveAdmin to prevent introduction of new warnings

Manually fix a `Lint/UselessAssignment` warning

Ref: activeadmin/activeadmin#8597

.rubocop.yml

@@ -48,6 +48,15 @@ Layout/TrailingWhitespace:
 Layout/TrailingEmptyLines:
   Enabled: true
 
+Lint/AmbiguousOperator:
+  Enabled: true
+
+Lint/AmbiguousRegexpLiteral:
+  Enabled: true
+
+Lint/UselessAssignment:
+  Enabled: true
+
 Minitest:
   Enabled: true
 

lib/inherited_resources/base_helpers.rb

@@ -297,7 +297,7 @@ def smart_resource_url
         if respond_to? :show
           url = resource_url rescue nil
         end
-        url ||= smart_collection_url
+        url || smart_collection_url
       end
 
       # URL to redirect to when redirect implies collection url.
@@ -309,7 +309,7 @@ def smart_collection_url
         if respond_to? :parent, true
           url ||= parent_url rescue nil
         end
-        url ||= root_url rescue nil
+        url || root_url rescue nil
       end
 
       # memoize the extraction of attributes from params