Fix to systemtest test_estimate_r2eff_err, after removing the possibility to use the chi2 Jacobian.
task #7822(https://gna.org/task/index.php?7822): Implement user function to estimate R2eff and associated errors for exponential curve fitting.
Authored by: tlinnet 2014-08-29
Parent: [r25469]
Child: [r25471]
