Fix deploy key api 500 if key is empty

lib/api/projects.rb

@@ -428,6 +428,7 @@ module API
       post ":id/keys" do
         attrs = attributes_for_keys [:title, :key]
 
+        if attrs[:key].present?
           attrs[:key].strip!
 
           # check if key already exist in project
@@ -444,6 +445,7 @@ module API
             present key, with: Entities::SSHKey
             return
           end
+        end
 
         key = DeployKey.new attrs