How to create multiple content_tags using safe_concat ?

I'm trying to concatenate multiple tags using content_tag and safe_concat, something like:

content_tag(:select, multiple: "multiple", :name => "contact[resources]") do
    content_tag(:optgroup, label: "LABEL", id: "some-id") do 
      safe_concat(
        if condition1
          (content_tag(:option, value: "val1") { "Val1" } )
        end
        if condition2
          (content_tag(:option, value: "val2") { "Val2" } )
        end              
      )
    end                
  end

But I keep getting the following error:

syntax error, unexpected keyword_if, expecting ')' 
syntax error, unexpected end-of-input, expecting keyword_end

you need to wrap every single output in safe_concat, like

content_tag(:select, multiple: "multiple", :name => "contact[resources]") do
  content_tag(:optgroup, label: "LABEL", id: "some-id") do 
    if condition1
      safe_concat(content_tag(:option, value: "val1") { "Val1" } )
    end
    if condition2
      safe_concat(content_tag(:option, value: "val2") { "Val2" } )
    end              
  end                
end