Check if link is an empty string when evaulating if replaceable

Signed-off-by: Mykola Mandra <mykola.mandra@cloudsoft.io>
diff --git a/_plugins/jekyll_relative_links.rb b/_plugins/jekyll_relative_links.rb
index 3beb138..852981b 100644
--- a/_plugins/jekyll_relative_links.rb
+++ b/_plugins/jekyll_relative_links.rb
@@ -238,7 +238,7 @@
     end
 
     def replaceable_link?(string)
-      !fragment?(string) && !absolute_url?(string)
+      !fragment?(string) && !absolute_url?(string) && string != ""
     end
 
     def option(key)