Skipping river calculation results in stone instead of ocean

[dkartaschew]

If river option is off, large ocean areas are filled with stone instead of being typical ocean/beach area.

Steps to replicate:

1. Download SRTM data for 39_01
2. run tool select SRTM data and world file.
3. Under region, leave as "Don't modify the image"
4. Uncheck to disable rivers, use all defaults.
5. Click on Proceed.
6. Wait for finish.
7. Open the world in minestest and starting location (0,0,0) is in all stone area. Flying around you find small islands on green in a sea of stone.

STRM data for grid 39_01 = http://srtm.csi.cgiar.org/SRT-ZIP/SRTM_V41/SRTM_Data_GeoTiff/srtm_39_01.zip.

[gaelysam]

I'll take a look at this.