Fix the exception handling for elevation download

[Hypercookie]

Describe the bug
When using the CGIARElevation provider, 0.0 will be returned for all queries.
This probably happens because the default base URL (https://srtm.csi.cgiar.org/) does time out now. (This is different from #2642). At least on my machine, this fails silently.
I don't know if this is only temporary or if this dataset has been removed.
To Reproduce

1. Create an instance of CGIARElevation.
2. Query the instance for any lat/long
3. 0.0 will be returned.
4. Look inside the cache folder. The files do exist, but they are corrupted

Expected behavior
The correct elevation should be returned. Or an exception must be thrown.

System Information

MacOS, OpenJDK 20.0.2, Graphopper 7.0

[otbutz]

Seems to be back up. But we need to fix the exception handling:

graphhopper/core/src/main/java/com/graphhopper/reader/dem/AbstractTiffElevationProvider.java

Lines 138 to 143 in 3bf387c

	} catch (IOException ex) {
	demProvider.setSeaLevel(true);
	// use small size on disc and in-memory
	heights.create(10).flush();
	return 0;
	}