DirectFunctionCall* crash when called directly from C code

[ezimanyi]

Functions that use SetSpatialRefSysSchema will crash when called directly from C code (like with DirectFunctionCall* and such). This patches adds a guard against that issue.

diff -urdN a/libpgcommon/lwgeom_transform.c b/libpgcommon/lwgeom_transform.c --- a/libpgcommon/lwgeom_transform.c 2018-01-16 06:31:17.000000000 +0100 +++ b/libpgcommon/lwgeom_transform.c 2018-03-05 14:29:47.644394250 +0100 @@ -740,6 +740,7 @@

if (!fcinfo

!fcinfo->flinfo) return;

nsp_name = get_namespace_name(get_func_namespace(fcinfo->flinfo->fn_oid));

+ if(!nsp_name) return ;

elog(DEBUG4, "%s located %s in namespace %s", func, get_func_name(fcinfo->flinfo->fn_oid), nsp_name);

spatialRefSysSchema = MemoryContextAlloc(CacheMemoryContext, strlen(nsp_name)+1);

[pramsey]

In 16542:

Guard against lookup failure, to avoid segfault in internally called case (references #4067)

[pramsey]

In 16543:

Guard against lookup failure, to avoid segfault in internally called case (closes #4067)