hotfix: continue instead of break from while if fread returns an empty string

Introduced in 461961f962ab70c63adfb78215fb66123605da7e

Breaking from the loop is causing the following exception:

    Consumer failure PhpAmqpLib\Exception\AMQPRuntimeException Exception 'Error reading data. Received 0 instead of expected 7 bytes':
    #0 /my/path/vendor/videlalvaro/php-amqplib/PhpAmqpLib/Wire/AMQPReader.php(128): PhpAmqpLib\Wire\IO\StreamIO->read(7)
    #1 /my/path/vendor/videlalvaro/php-amqplib/PhpAmqpLib/Wire/AMQPReader.php(88): PhpAmqpLib\Wire\AMQPReader->rawread(7)
    #2 /my/path/vendor/videlalvaro/php-amqplib/PhpAmqpLib/Connection/AbstractConnection.php(311): PhpAmqpLib\Wire\AMQPReader->read(7)
    #3 /my/path/vendor/videlalvaro/php-amqplib/PhpAmqpLib/Connection/AbstractConnection.php(344): PhpAmqpLib\Connection\AbstractConnection->wait_frame(0)
    #4 /my/path/vendor/videlalvaro/php-amqplib/PhpAmqpLib/Channel/AbstractChannel.php(121): PhpAmqpLib\Connection\AbstractConnection->wait_channel(1, 0)
    #5 /my/path/vendor/videlalvaro/php-amqplib/PhpAmqpLib/Channel/AbstractChannel.php(229): PhpAmqpLib\Channel\AbstractChannel->next_frame(0)

I believe because a string can be a valid data block transferred in and of itself. Merely continuing instead of breaking until the feof() fixes the problem on my version of Rabbit:

RabbitMQ 3.1.5, Erlang R14B04