Reporting: fix crash when xrange argument of addGraph() is missing

(cherry picked from commit e2a11a1a)
9 jobs for 4.7 in 268 minutes and 5 seconds (queued for 14 seconds)
Status Name Job ID Coverage
  Build
passed build_binaries #34405

00:11:22

passed build_doc #34406

00:01:25

 
  Test
passed test_dynare++ #34410

00:16:59

passed test_matlab #34407

01:17:53

passed test_octave #34409

04:16:39

passed test_old_matlab #34408

02:54:39

 
  Pkg
passed pkg_macOS #34413
macOS

00:21:00

passed pkg_source #34411

00:01:28

passed pkg_windows #34412

00:12:00