"Value must be a scalar ENVIRaster"
Do a print statement on the result of this raster - does it return an array? It must be a scalar.

So what I have to do with my model in this particular case?

You have to pass a single raster rather than an array. So, if you want to pass the first raster of an array of rasters:

input_raster=raster[0]

or similar depending on what your raster object returns.

Yes, I understand. But I don't use IDL, I know only modeler.
I have to use iterator and Extract Element because I have 10 multi spectral raster after DOS and 10 panchromatic after DOS too.
I don't have a problem when I process two different models: one for DOS and one for pan sharpening. But I would like to combine these in one model and run everything once.

Yes, you need to use Extract Bands from Raster to extract one of the rasters from your open raster. However you will need to figure out exactly what you are passing. Why is a multiband high resolution raster passed to this routine? Did you stack them into a file?

I made separate models for the Dark Subtraction model, separately for multispectral and panchromatic bands. Now I would like to combine these models into one and add NNDiffuse PS functions to it.
I don't have a problem when I process two different models: one for DOS and one for pan sharpening. But I would like to combine these in one model and run everything once.
I think that the issue is caused by the Aggregator and Extract Elements From Array. But I don't know how to change it.
Still I get the error: "Parameter INPUT_HIGH_RESOLUTION_RASTER faild validation: Value must be a scalar ENVIRaster".

In IDL the model looks like below:

; -----------------------------
; Generated by the ENVI Modeler
; ENVI 5.5.1, API 3.3
; -----------------------------
pro MyProgram
compile_opt idl2, hidden
on_error, 2

aggregator_1 = Dictionary()
list_aggregator_1 = List()

aggregator_2 = Dictionary()
list_aggregator_2 = List()

; --------
; Iterator
; --------
foreach iterator_2, raster_2, iterator_2_index do begin

; -----------------
; Generate Filename
; -----------------
task_8 = ENVITask('GenerateFilename')
task_8.number = iterator_2_index
task_8.directory = "C:\"
task_8.prefix = 'DSM_PAN_'
task_8.random = !false
task_8.Execute

; -----------------------
; Radiometric Calibration
; -----------------------
task_5 = ENVITask('RadiometricCalibration')
task_5.input_raster = iterator_2
task_5.Execute

; -----------------
; Raster Statistics
; -----------------
task_6 = ENVITask('RasterStatistics')
task_6.input_raster = task_5.output_raster
task_6.Execute

; ---------------------------
; Dark Subtraction Correction
; ---------------------------
task_7 = ENVITask('DarkSubtractionCorrection')
task_7.values = task_6.min
task_7.input_raster = task_5.output_raster
task_7.output_raster_uri = task_8.output_filename
task_7.Execute

; ----------
; Aggregator
; ----------
list_aggregator_2.Add, task_7.output_raster, /EXTRACT
aggregator_2.output = list_aggregator_2

endforeach

; --------
; Iterator
; --------
foreach iterator_1, raster_1, iterator_1_index do begin

; -----------------
; Generate Filename
; -----------------
task_4 = ENVITask('GenerateFilename')
task_4.number = iterator_1_index
task_4.directory = "C:\"
task_4.prefix = 'DSM_'
task_4.random = !false
task_4.Execute

; -----------------------
; Radiometric Calibration
; -----------------------
task_1 = ENVITask('RadiometricCalibration')
task_1.input_raster = iterator_1
task_1.Execute

; -----------------
; Raster Statistics
; -----------------
task_2 = ENVITask('RasterStatistics')
task_2.input_raster = task_1.output_raster
task_2.Execute

; ---------------------------
; Dark Subtraction Correction
; ---------------------------
task_3 = ENVITask('DarkSubtractionCorrection')
task_3.values = task_2.min
task_3.input_raster = task_1.output_raster
task_3.output_raster_uri = task_4.output_filename
task_3.Execute

; ----------
; Aggregator
; ----------
list_aggregator_1.Add, task_3.output_raster, /EXTRACT
aggregator_1.output = list_aggregator_1

endforeach

; --------
; Iterator
; --------
foreach iterator_3, aggregator_1.output, iterator_3_index do begin

; -----------------
; Generate Filename
; -----------------
task_10 = ENVITask('GenerateFilename')
task_10.number = iterator_3_index
task_10.directory = "C:\"
task_10.prefix = 'PAN_SH_'
task_10.random = !false
task_10.Execute

; ---------------------------
; Extract Elements from Array
; ---------------------------
elementExtractor_1 = Dictionary()
elementExtractor_1.output_element = aggregator_2.output[[iterator_3_index]]

; ------------------------
; NNDiffuse Pan Sharpening
; ------------------------
task_9 = ENVITask('NNDiffusePanSharpening')
task_9.output_raster_uri = task_10.output_filename
task_9.input_low_resolution_raster = iterator_3
task_9.input_high_resolution_raster = elementExtractor_1.output_element
task_9.Execute

endforeach

end