Improve handling when the continuum of the fitted line has not enough points/scatter and reaches very high S/N ratios

[Abelink23]

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Analyzing spectrum: HD155416_20230723_043512_F_V48000.fits
SNR continuum for 4351.768A is very high. Set to 1000
SNR continuum for 6456.383A is very high. Set to 1000

RV0=-9.95 (5/10 lines used with std=0.24 [km/s])
SNR continuum for 4351.768A is very high. Set to 1000
SNR continuum for 4508.288A is very high. Set to 1000
SNR continuum for 4815.552A is very high. Set to 1000
SNR continuum for 5018.440A is very high. Set to 1000
SNR continuum for 5260.259A is very high. Set to 1000
SNR continuum for 5362.869A is very high. Set to 1000
SNR continuum for 5432.797A is very high. Set to 1000
SNR continuum for 5473.614A is very high. Set to 1000
SNR continuum for 5978.930A is very high. Set to 1000
SNR continuum for 6247.557A is very high. Set to 1000
SNR continuum for 6347.110A is very high. Set to 1000
SNR continuum for 6371.370A is very high. Set to 1000
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