This is related to commit e0d38ba3f912b7ae6b34e66a44e529ec37394458. In case
we have to deal with an inconsitent raster where the nodata value is set to
a value not representable in the data type, ignore it. Otherwise, a NaN value
in a Byte raster would be cast as 0.
Currently if the source raster has no nodata value, the writer will still write
nan as the output nodata value, ignoring the flag that specifies if there is a
nodata value or not. On a raster with byte data type, this will cause
confusion on reading since the nodata value will be somehow cast as 0.
Make QgsRasterChecker check for nodata consistency between source and target, and
add a test file that shows the issue.
