Merge branch 'discret_error_message' into 'master'

discretionary_policy_1.m: check for NaN before checking for non-zero derivatives

See merge request !1644
5 jobs for master in 71 minutes and 55 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Build
passed #2737
build_binaries

00:08:41

passed #2738
build_doc

00:01:53

 
  Test
passed #2741
test_dynare++

00:07:31

passed #2739
testsuite_matlab

01:03:13

manual #2740
allowed to fail manual
testsuite_octave_manual