In a nested \if, if the first if doesn't match, the nesting isn't properly parsed.

Example document:
---------------
/**
\mainpage

Test
*/

/**
\if DOCUMENT_A
\page Page1 Page 1

\if DOCUMENT_B
Test text 1
\endif

Test text 2
\endif
*/

/**
\page Page2 Page 2
 
Test text 3
 
*/
---------------

Using ENABLED_SECTIONS = B, doxygen generates only the Page 2, but Page 2 contains the strings:
Test text 2  <=== This shouldn't be there!
Test text 3