Several fuzzer generated tests trigger crashes/asserts because the OuterStripMinedLoopEnd main_head->outer_loop()->outer_loop_tail() only has an IfTrue projection.

For example, with attached SDD87.java we fail because sfpt = head->as_Loop()->outer_safepoint() is
NULL, because loop->_head->outer_loop_tail() only has an IfTrue projection:

# A fatal error has been detected by the Java Runtime Environment:
#
# SIGSEGV (0xb) at pc=0x00007fdf1d8794ec, pid=9384, tid=9397
#
# JRE version: Java(TM) SE Runtime Environment (18.0) (fastdebug build 18-internal+0-2021-07-15-1125012.tobias...)
# Java VM: Java HotSpot(TM) 64-Bit Server VM (fastdebug 18-internal+0-2021-07-15-1125012.tobias..., mixed mode, tiered, compressed oops, compressed class ptrs, g1 gc, linux-amd64)
# Problematic frame:
# V [libjvm.so+0x12bb4ec] Node::in(unsigned int) const [clone .constprop.1]+0xc
#
# Core dump will be written. Default location: Core dumps may be processed with "/usr/share/apport/apport %p %s %c %d %P %E" (or dumping to /home/tobias/Downloads/32703210/core.9384)
#
# If you would like to submit a bug report, please visit:
# https://bugreport.java.com/bugreport/crash.jsp
#

--------------- S U M M A R Y ------------

Command Line: SDD87

Host: prometheus, Intel(R) Core(TM) i7-9850H CPU @ 2.60GHz, 12 cores, 31G, Ubuntu 20.04.2 LTS
Time: Mon Jul 19 08:47:12 2021 CEST elapsed time: 0.285794 seconds (0d 0h 0m 0s)

--------------- T H R E A D ---------------

Current thread (0x00007fdf182ed9e0): JavaThread "C2 CompilerThread0" daemon [_thread_in_native, id=9397, stack(0x00007fdee5739000,0x00007fdee583a000)]


Current CompileTask:
C2: 285 283 ! 4 SDD87::mainTest (845 bytes)

Stack: [0x00007fdee5739000,0x00007fdee583a000], sp=0x00007fdee58341a0, free space=1004k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x12bb4ec] Node::in(unsigned int) const [clone .constprop.1]+0xc
V [libjvm.so+0x12cfbc3] PhaseIdealLoop::verify_strip_mined_scheduling(Node*, Node*)+0x93
V [libjvm.so+0x12dd0f2] PhaseIdealLoop::build_loop_late_post_work(Node*, bool)+0x122
V [libjvm.so+0x12dd77a] PhaseIdealLoop::build_loop_late(VectorSet&, Node_List&, Node_Stack&)+0xba
V [libjvm.so+0x12de0e7] PhaseIdealLoop::build_and_optimize(LoopOptsMode)+0x507
V [libjvm.so+0x9fb46c] PhaseIdealLoop::optimize(PhaseIterGVN&, LoopOptsMode)+0x28c
V [libjvm.so+0x9f7d5f] Compile::Optimize()+0x127f
V [libjvm.so+0x9f9a24] Compile::Compile(ciEnv*, ciMethod*, int, bool, bool, bool, bool, bool, DirectiveSet*)+0x1564
V [libjvm.so+0x819aa6] C2Compiler::compile_method(ciEnv*, ciMethod*, int, bool, DirectiveSet*)+0x646
V [libjvm.so+0xa0a4e9] CompileBroker::invoke_compiler_on_method(CompileTask*)+0xef9
V [libjvm.so+0xa0b218] CompileBroker::compiler_thread_loop()+0x598
V [libjvm.so+0x186728c] JavaThread::thread_main_inner()+0x27c
V [libjvm.so+0x186da30] Thread::call_run()+0x100
V [libjvm.so+0x1550bf4] thread_native_entry(Thread*)+0x104

These issues were reported by John Jiang (johnsjiang@tencent.com)