divide by zero in SSRS

I have this exp for a calculated column in my Report “=Fields!email_subscribers.Value / Fields!TSA.Value”

but at runtime I get the warning below:

Warning 1 [rsRuntimeErrorInExpression] The Value expression for the textrun ‘EmailDB_as_Percentage_TSA.Paragraphs[0].TextRuns[0]’ contains an error: Attempted to divide by zero. 

Also at the Report output I get "#Error" sign  on the roll where “TSA” is “O”.  

Please what is the exp for “divide by Zero” on this?

Thanks