+proj=deformation crashes when passed points outside model area

[kbevers]

PROJ segfaults when trying to transform a point outside the defined area of the grids used in deformation as seen in the example below that uses the velocity model from the proj-datumgrids-europe package. The grid has a bounding box spanned by the points 3,53 (LL) and 40,74 (UR).

echo 12 50 0 0 | ./bin/cct  +proj=pipeline +ellps=GRS80 \
+step   +proj=cart \
+step   +proj=deformation +t_epoch=200.0 \
+xy_grids=nkgrf03vel_realigned_xy.ct2 \
+z_grids=nkgrf03vel_realigned_z.gtx \
+step   +proj=cart +inv
Segmentation fault: 11

A temporary fix is to make the grids optional and add the null grid:

+proj=deformation +t_epoch=200.0
+xy_grids=@nkgrf03vel_realigned_xy.ct2,@null
+z_grids=@nkgrf03vel_realigned_z.gtx,@null