ActiveUp.Net.Imap4: Imap4Client now throws an exception if the stream returns null,

preventing the receive code from looping for ever and ending in an OutOfMemoryException

Author: Alprema_cp

Class Library/ActiveUp.Net.Imap4/Imap4Client.cs

@@ -1147,6 +1147,8 @@ public string Command(string command, string stamp, CommandOptions options = nul
                         break;
                     }
                 }
+                else
+                    throw new Imap4Exception("Unexpected end of stream");
             }
             var bufferString = buffer.ToString();