Converting string to float for null value System.FormatException: Input string was not in a correct format in ASP.Net

this code below supposed to show amount from column amountpaid, but if the column is empty when you call the column data on the lable it throws this error below

Server Error in '/' Application.
Input string was not in a correct format.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.FormatException: Input string was not in a correct format.

Source Error:



Line 122:                       float balanceavailable = float.Parse(lblbalance.Text.Trim());
Line 123:                      
Line 124:                      // int amountavailable = lblAmountUpdate);

please how do i prevent the error when the lable is empty