Failed to call method "Initialize" for indicator 'Test': Object reference not set to

[clearpicks]

In my indicator script, in Initialize(), I need to access information of the time frame and intrument name so that the indicator can be customized according to the timeframe and instrument information. For example, if the indicator is running on a daily chart, two plots need to be added to display bollinger while on intraday chart ADD(Plot) should not be called in initialization. So in Initialize(), I use
isOnDailyChart = Bars.Period.Id == PeriodType.Day && Bars.Period.Value == 1;
symbol = Instrument.MasterInstrument.Name;
to access timeframe and symbol information. However each time in NT Log window I get an error message:

Failed to call method "Initialize" for indicator 'Test': Object reference not set to an instance of an object.

Although this error message seems not affecting the correct running of my indicator, there may be a lot such error message when I swtich timeframe and symbol frequently, which is quite annoying.

My question is whether I should access the member variables of Bars and Instrument? Why does my indicator work fine with such error message?
What is the correct way to access time frame and instrument information within Initialize() function?

[NinjaTrader_Dierk]

- you can't access neither Instrument nor Bars in Initialize()
- try BarsPeriod instead

[clearpicks]

BarsPeriod only works for StrategyBase not IndicatorBase.

Is there any method to create different number of plots or lines using ADD(Plot) and ADD(Line) based on the timeframe and the primary instrument information? If I move those initialization code in Initialize() to OnBarUpdate() with flag defined to make sure the initialization part only executed once, shall I encounter any error? Is my work around solution correct?

- you can't access neither Instrument nor Bars in Initialize()
- try BarsPeriod instead

[NinjaTrader_Dierk]

These are the limitations plus you only can call Add in Initialize()