When we need to generate a Excel file with a logo file the library throws a null pointer

[pablo-gago]

Describe the bug
As is the same code to generate a pdf and generate an excel file. The PDF file is generated with a logo image. But when the Excel file is generated the library throws an exception (java.io.FileNotFoundException: img\ics.png (The system cannot find the path specified)).

This exception is throwed by SummarySheetTemplate in the method addTitle when try get logo path file.

The same code generating pdf is working fine.

To Reproduce
Steps to reproduce the behavior:

1. In method buildHeaderConfiguration add logo path (.logoPath("img/ics.png")
   
2. Execute a test to create a excel file with logopath
3. Exception java.io.FileNotFoundException: img\ics.png (The system cannot find the path specified)

Expected behavior
Generate a Excel file without issues.

Screenshots

• PDF
  

Desktop (please complete the following information):

• Version 1.8.2

Additional context