fix: Add blank check for file param in Import API (#3057)

config/locales/en.yml

@@ -41,6 +41,9 @@ en:
       invalid_email: You have entered an invalid email
       email_already_exists: "You have already signed up for an account with %{email}"
       failed: Signup failed
+    contacts:
+      import:
+        failed: File is blank  
 
   reports:
     period: Reporting period %{since} to %{until}