#1 no check for malloc() result at catPoly.cpp causes SEGFAULT

[Mikhail Titov]

PIHMgis fails to convert catchments from raster to polygons for large grids. It is not obvious that there is a limitation on the size.

malloc() result should be checked at least at C:\QGIS_Native\qgis_1.0.3\src\plugins\pihm_gis\pihmRasterLIBS\catPoly.cpp line 80 and user should be warned. Or even better to warn user who tries to work with fine resolution DEM.