Deal with read_nonblock returning nil early

lib/puma/client.rb

@@ -284,6 +284,14 @@ module Puma
         raise ConnectionError, "Connection error detected during read"
       end
 
+      # No data means a closed socket
+      unless data
+        @buffer = nil
+        @requests_served += 1
+        @ready = true
+        raise EOFError
+      end
+
       if @buffer
         @buffer << data
       else
@@ -313,6 +321,14 @@ module Puma
           raise e
         end
 
+        # No data means a closed socket
+        unless data
+          @buffer = nil
+          @requests_served += 1
+          @ready = true
+          raise EOFError
+        end
+
         if @buffer
           @buffer << data
         else