title: Pandas Data Reader Tiingo Errors when pulling multiple symbols if one symbol does not exist or is delisted
body: <p>I am writing an app to track stock data entered into a spreadsheet.
  I currently have it working by making a call to <code>pandas_datareader.tiingo.TiingoDailyReader</code> for every symbol.
  The data reader is capable of taking a list of symbols and pulling all the data for those symbols at once.
  I prefer this because I can make one call then query the dataframe it returns.</p>
  
  <p>The issue I'm running into is when a symbol is delisted or does not exist this causes the entire call to fail resulting in an empty dataframe.
  I've worked around this a little bit by checking all the symbols against a list of supported symbols for Tiingo.
  However, this is not perfect as I have run into a instances where a symbol is supported but does not have data for the dates I request.</p>
  
  <p>Is there a way to call all the symbols at once and have the data reader skip these errors or return no data for the problem symbol?</p>
  
  <p>Thanks,</p>