Fix certificate validators

app/validators/certificate_key_validator.rb

@@ -16,7 +16,7 @@ class CertificateKeyValidator < ActiveModel::EachValidator
   private
 
   def valid_private_key_pem?(value)
-    return unless value
+    return false unless value
     pkey = OpenSSL::PKey::RSA.new(value)
     pkey.private?
   rescue OpenSSL::PKey::PKeyError

app/validators/certificate_validator.rb

@@ -16,9 +16,9 @@ class CertificateValidator < ActiveModel::EachValidator
   private
 
   def valid_certificate_pem?(value)
-    return unless value
-    OpenSSL::X509::Certificate.new(value)
+    return false unless value
+    OpenSSL::X509::Certificate.new(value).present?
   rescue OpenSSL::X509::CertificateError
-    nil
+    false
   end
 end