fix: handle empty string for CAPTAIN_OPEN_AI_ENDPOINT config (#12435)

When CAPTAIN_OPEN_AI_ENDPOINT is set to empty string, use .presence to
properly fall back to default OpenAI endpoint instead of creating
malformed URLs.

Fixes #12383

Co-authored-by: Pranav <pranav@chatwoot.com>

lib/integrations/openai_base_service.rb

@@ -81,7 +81,7 @@ class Integrations::OpenaiBaseService
   end
 
   def api_url
-    endpoint = InstallationConfig.find_by(name: 'CAPTAIN_OPEN_AI_ENDPOINT')&.value || 'https://api.openai.com/'
+    endpoint = InstallationConfig.find_by(name: 'CAPTAIN_OPEN_AI_ENDPOINT')&.value.presence || 'https://api.openai.com/'
     endpoint = endpoint.chomp('/')
     "#{endpoint}/v1/chat/completions"
   end