verbatim blocks are not formatted as blocks when first line starts with blanks

Steps to reproduce:

1. paste the following text in a zim page (note the blanks in front of the first line)

   ensemble avg p90 p95
1 ctrl0 6.685526 7.047663 7.073926
2 ctrl1 7.229837 7.608090 7.656541

2. Select the three lines and format them as verbatim.

I would expect the three lines to get formatted as verbatim block

'''
   ensemble avg p90 p95
1 ctrl0 6.685526 7.047663 7.073926
2 ctrl1 7.229837 7.608090 7.656541
'''

instead each line is formatted as a single verbatim line and the

  ''ensemble avg p90 p95''
''1 ctrl0 6.685526 7.047663 7.073926''
''2 ctrl1 7.229837 7.608090 7.656541''