Don't segfault when running atexit before jl_threads_init

Author: vchuravy

src/gc.c

@@ -481,9 +481,11 @@ static void schedule_all_finalizers(arraylist_t *flist) JL_NOTSAFEPOINT
 void jl_gc_run_all_finalizers(jl_task_t *ct)
 {
     schedule_all_finalizers(&finalizer_list_marked);
+    // This could be run before we had a chance to setup all threads
     for (int i = 0;i < jl_n_threads;i++) {
         jl_ptls_t ptls2 = jl_all_tls_states[i];
-        schedule_all_finalizers(&ptls2->finalizers);
+        if (ptls2)
+            schedule_all_finalizers(&ptls2->finalizers);
     }
     run_finalizers(ct);
 }

test/cmdlineargs.jl

@@ -249,6 +249,9 @@ let exename = `$(Base.julia_cmd()) --startup-file=no --color=no`
         @test read(`$exename -p2 -t2 -e $code`, String) == "6"
     end
 
+    # Combining --threads and invalid -C should yield a decent error
+    @test !success(`$exename -t 2 -C invalidtarget`)
+
     # --procs
     @test readchomp(`$exename -q -p 2 -e "println(nworkers())"`) == "2"
     @test !success(`$exename -p 0`)