FIX: Handle files removed between `glob` and `mtime`

FIX: Handle files removed between glob and mtime

diff --git a/lib/file_store/base_store.rb b/lib/file_store/base_store.rb
index df85960..4832776 100644
--- a/lib/file_store/base_store.rb
+++ b/lib/file_store/base_store.rb
@@ -151,8 +151,14 @@ module FileStore
 
       # Remove all but CACHE_MAXIMUM_SIZE most recent files
       files = Dir.glob("#{CACHE_DIR}*")
-        .sort_by { |f| File.mtime(f) }
-        .slice(0...-CACHE_MAXIMUM_SIZE)
+      files.sort_by! do |file|
+        begin
+          File.mtime(file)
+        rescue Errno::ENOENT
+          Time.new(0)
+        end
+      end
+      files.pop(CACHE_MAXIMUM_SIZE)
 
       FileUtils.rm(files, force: true)
     end

GitHub sha: 7df688d1