Don't break on icon size "any"

... and any other strings failing to match the "sizes" number format
for that matter

lib/manifique/metadata.rb

@@ -47,7 +47,7 @@ module Manifique
       end
 
       if options[:sizes]
-        results.reject! { |r| r["sizes"].nil? }
+        results.reject! { |r| r["sizes"].nil? || r["sizes"].match(/(\d+)x/).nil? }
         results.sort!   { |a, b| sizes_to_i(b["sizes"]) <=> sizes_to_i(a["sizes"]) }
 
         if icon = select_exact_size(results, options[:sizes])