fuzzing: empty RLum.Data.Image

[mcol]

This script:

what <- set_RLum("RLum.Data.Image")
fuzz(funs, what, ignore.patterns = NULL, ignore.warnings = TRUE)

Produces:

	🚨   CAUGHT BY THE FUZZ!   🚨

FAIL: merge_RLum.Analysis ( RLum.Data.Image )
    NA/NaN argument

FAIL: merge_RLum.Data.Curve ( RLum.Data.Image )
    NA/NaN argument

FAIL: merge_RLum.Data.Spectrum ( RLum.Data.Image )
    NA/NaN argument

FAIL: plot_RLum ( RLum.Data.Image )
    NA/NaN argument

FAIL: plot_RLum.Data.Image ( RLum.Data.Image )
    NA/NaN argument

FAIL: trim_RLum.Data ( RLum.Data.Image )
    NA/NaN argument

FAIL: view ( RLum.Data.Image )
    invalid 'x' argument

FAIL: write_R2TIFF ( RLum.Data.Image )
    image must be a matrix or an array of two or three dimensions

Part of #439.