@dseries/{first,last}observedperiod.m: MATLAB R2009b compatibility fix

prod() does not accept logical arrays, need to explicitly convert to doubles.
3 jobs for master in 1 minute and 35 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #6465
testsuite_matlab

00:00:54

failed #6467
allowed to fail
testsuite_octave

00:01:33

failed #6466
allowed to fail
testsuite_old_matlab

00:00:47

 
Name Stage Failure
failed
testsuite_octave Test
/home/gitlab-runner/builds/79277319/0/sebastien/dseries/tests/../src/utilities/x13/printoption.m                                      Unit test number  1  PASS    [  0.0231359 ]
/home/gitlab-runner/builds/79277319/0/sebastien/dseries/tests/../src/utilities/x13/printspan.m Unit test number 1 PASS [ 0.00919199 ]
/home/gitlab-runner/builds/79277319/0/sebastien/dseries/tests/../src/utilities/x13/printspan.m Unit test number 2 PASS [ 0.00810313 ]
/home/gitlab-runner/builds/79277319/0/sebastien/dseries/tests/../src/utilities/x13/printspan.m Unit test number 3 PASS [ 0.00746202 ]
/home/gitlab-runner/builds/79277319/0/sebastien/dseries/tests/../src/utilities/x13/printstart.m Unit test number 1 PASS [ 0.00612998 ]
/home/gitlab-runner/builds/79277319/0/sebastien/dseries/tests/../src/utilities/x13/setdefaultmember.m Unit test number 1 PASS [ 0.00369191 ]

make: *** [Makefile:10: check-octave] Error 1
ERROR: Job failed: exit status 1
failed
testsuite_old_matlab Test
/home/gitlab-runner/builds/a354a37e/0/sebastien/dseries/tests/../src/utilities/x13/printoption.m                                      Unit test number  1  PASS    [  0.01039 ]
/home/gitlab-runner/builds/a354a37e/0/sebastien/dseries/tests/../src/utilities/x13/printspan.m Unit test number 1 PASS [ 0.004418 ]
/home/gitlab-runner/builds/a354a37e/0/sebastien/dseries/tests/../src/utilities/x13/printspan.m Unit test number 2 PASS [ 0.002685 ]
/home/gitlab-runner/builds/a354a37e/0/sebastien/dseries/tests/../src/utilities/x13/printspan.m Unit test number 3 PASS [ 0.002589 ]
/home/gitlab-runner/builds/a354a37e/0/sebastien/dseries/tests/../src/utilities/x13/printstart.m Unit test number 1 PASS [ 0.002052 ]
/home/gitlab-runner/builds/a354a37e/0/sebastien/dseries/tests/../src/utilities/x13/setdefaultmember.m Unit test number 1 PASS [ 0.002319 ]

make: *** [Makefile:14: check-matlab] Error 1
ERROR: Job failed: exit status 1