"New schematisation" wizard: check if DEM and friction files actually exist

[leendertvanwolfswinkel]

On the last page of the wizard: If user has chosen a DEM and/or friction file and clicks "Create Schematisation", please check if the files exist and are .tif / .tiff files. If not, show message "Chosen DEM file does not exist or is not a GeoTIFF (.tif or .tiff)" / "Chosen friction file does not exist or is not a GeoTIFF (.tif or .tiff)"

Screenshots from a video a user sent us:

[Overmeen]

The behavior is not entirely as expected.

In case a "Global 2D friction coefficient" is set to a (non-zero) value and the "Friction file" field is left empty, the user meant to add the global value. There should not be a pop-up message indicating the friction file does not exist.

The behavior should be:

• If "Friction file" field is empty and "Global 2D friction coefficient" is set to a (non-zero) value > create schematisation with Global value
• If "Friction file" field is empty and "Global 2D friction coefficient" is empty or zero > pop-message "'Global 2D friction coefficient' value has to be greater than 0
• If "Friction file" field is not empty > check for file existence and validity file extension > if ok, create schematisation with friction file. If not, pop-up message "Chosen friction file does not exist or is not a GeoTIFF (.tif or .tiff)"

[ldebek]

@Overmeen Changes in the validation rules applied.

[leendertvanwolfswinkel]

@ldebek similar validation rules should also be applied to the DEM: The behavior should be: If "Digital elevation model" field is empty, create schematisation without reference to a DEM file If "Digital elevation model" field is not empty, check for file existence and validity file extension > if ok, create schematisation with dem file. If not, pop-up message "Chosen DEM file does not exist or is not a GeoTIFF (.tif or .tiff)"

[ldebek]

Changes applied.