Correct a function pre/postcondition [PR102403].

Resolves:
PR middle-end/102403 - ICE in init_from_control_deps, at gimple-predicate-analysis.cc:2364

gcc/ChangeLog:
	PR middle-end/102403
	* gimple-predicate-analysis.cc (predicate::init_from_control_deps):
	Correct a function pre/postcondition.

gcc/testsuite/ChangeLog:
	PR middle-end/102403
	* gcc.dg/uninit-pr102403.c: New test.
	* gcc.dg/uninit-pr102403-c2.c: New test.