Fix Selenium errors handling

Do not check for `sessionId` in Selenium responses, because some errors does not have it.

For example:

```js
{
  "status":13,
  "value":{
    "message":"Session [f90c948b-ddf0-46d2-b0f0-8852dd26802f] was terminated due to BROWSER_TIMEOUT",
    "class":"org.openqa.grid.common.exception.GridException",
    "stackTrace":[
      {
        "fileName":"ActiveTestSessions.java",
        "lineNumber":104,
        "className":"org.openqa.grid.internal.ActiveTestSessions",
        "methodName":"getExistingSession"
      },
      {
        "fileName":"Registry.java",
        "lineNumber":423,
        "className":"org.openqa.grid.internal.Registry",
        "methodName":"getExistingSession"
      },
      {
        "fileName":"RequestHandler.java",
        "lineNumber":235,
        "className":"org.openqa.grid.web.servlet.handler.RequestHandler",
        "methodName":"getSession"
      },
      {
        "fileName":"RequestHandler.java",
        "lineNumber":117,
        "className":"org.openqa.grid.web.servlet.handler.RequestHandler",
        "methodName":"process"
      },
      {
        "fileName":"DriverServlet.java",
        "lineNumber":84,
        "className":"org.openqa.grid.web.servlet.DriverServlet",
        "methodName":"process"
      },
      {
        "fileName":"DriverServlet.java",
        "lineNumber":74,
        "className":"org.openqa.grid.web.servlet.DriverServlet",
        "methodName":"doDelete"
      },
      {
        "fileName":"HttpServlet.java",
        "lineNumber":733,
        "className":"javax.servlet.http.HttpServlet",
        "methodName":"service"
      },
      {
        "fileName":"HttpServlet.java",
        "lineNumber":820,
        "className":"javax.servlet.http.HttpServlet",
        "methodName":"service"
      },
      {
        "fileName":"ServletHolder.java",
        "lineNumber":565,
        "className":"org.seleniumhq.jetty7.servlet.ServletHolder",
        "methodName":"handle"
      },
      {
        "fileName":"ServletHandler.java",
        "lineNumber":479,
        "className":"org.seleniumhq.jetty7.servlet.ServletHandler",
        "methodName":"doHandle"
      },
      {
        "fileName":"SessionHandler.java",
        "lineNumber":225,
        "className":"org.seleniumhq.jetty7.server.session.SessionHandler",
        "methodName":"doHandle"
      },
      {
        "fileName":"ContextHandler.java",
        "lineNumber":1031,
        "className":"org.seleniumhq.jetty7.server.handler.ContextHandler",
        "methodName":"doHandle"
      },
      {
        "fileName":"ServletHandler.java",
        "lineNumber":406,
        "className":"org.seleniumhq.jetty7.servlet.ServletHandler",
        "methodName":"doScope"
      },
      {
        "fileName":"SessionHandler.java",
        "lineNumber":186,
        "className":"org.seleniumhq.jetty7.server.session.SessionHandler",
        "methodName":"doScope"
      },
      {
        "fileName":"ContextHandler.java",
        "lineNumber":965,
        "className":"org.seleniumhq.jetty7.server.handler.ContextHandler",
        "methodName":"doScope"
      },
      {
        "fileName":"ScopedHandler.java",
        "lineNumber":117,
        "className":"org.seleniumhq.jetty7.server.handler.ScopedHandler",
        "methodName":"handle"
      },
      {
        "fileName":"HandlerWrapper.java",
        "lineNumber":111,
        "className":"org.seleniumhq.jetty7.server.handler.HandlerWrapper",
        "methodName":"handle"
      },
      {
        "fileName":"Server.java",
        "lineNumber":345,
        "className":"org.seleniumhq.jetty7.server.Server",
        "methodName":"handle"
      },
      {
        "fileName":"AbstractHttpConnection.java",
        "lineNumber":452,
        "className":"org.seleniumhq.jetty7.server.AbstractHttpConnection",
        "methodName":"handleRequest"
      },
      {
        "fileName":"BlockingHttpConnection.java",
        "lineNumber":47,
        "className":"org.seleniumhq.jetty7.server.BlockingHttpConnection",
        "methodName":"handleRequest"
      },
      {
        "fileName":"AbstractHttpConnection.java",
        "lineNumber":884,
        "className":"org.seleniumhq.jetty7.server.AbstractHttpConnection",
        "methodName":"headerComplete"
      },
      {
        "fileName":"AbstractHttpConnection.java",
        "lineNumber":938,
        "className":"org.seleniumhq.jetty7.server.AbstractHttpConnection$RequestHandler",
        "methodName":"headerComplete"
      },
      {
        "fileName":"HttpParser.java",
        "lineNumber":634,
        "className":"org.seleniumhq.jetty7.http.HttpParser",
        "methodName":"parseNext"
      },
      {
        "fileName":"HttpParser.java",
        "lineNumber":230,
        "className":"org.seleniumhq.jetty7.http.HttpParser",
        "methodName":"parseAvailable"
      },
      {
        "fileName":"BlockingHttpConnection.java",
        "lineNumber":66,
        "className":"org.seleniumhq.jetty7.server.BlockingHttpConnection",
        "methodName":"handle"
      },
      {
        "fileName":"SocketConnector.java",
        "lineNumber":254,
        "className":"org.seleniumhq.jetty7.server.bio.SocketConnector$ConnectorEndPoint",
        "methodName":"run"
      },
      {
        "fileName":"QueuedThreadPool.java",
        "lineNumber":599,
        "className":"org.seleniumhq.jetty7.util.thread.QueuedThreadPool",
        "methodName":"runJob"
      },
      {
        "fileName":"QueuedThreadPool.java",
        "lineNumber":534,
        "className":"org.seleniumhq.jetty7.util.thread.QueuedThreadPool$3",
        "methodName":"run"
      },
      {
        "fileName":"Thread.java",
        "lineNumber":744,
        "className":"java.lang.Thread",
        "methodName":"run"
      }
    ]
  }
}
```