analyzer: fix ICE on function pointer casts [PR 93775]

analyzer: fix ICE on function pointer casts [PR 93775]

PR analyzer/93775 reports an ICE in cgraph_node::get when -fanalyzer is
used on code that calls a function pointer that was generated via a cast
from a non-function.

This patch fixes it by bulletproofing region_model::get_fndecl_for_call
for the case where the code_region's get_tree_for_child_region returns
NULL.

gcc/analyzer/ChangeLog:
	PR analyzer/93775
	* region-model.cc (region_model::get_fndecl_for_call): Handle the
	case where the code_region's get_tree_for_child_region returns
	NULL.

gcc/testsuite/ChangeLog:
	PR analyzer/93775
	* gcc.dg/analyzer/20020129-1.c: New test.