When plpgsql_check is loaded due dependency on execution of some function,

then fmgr hook can be installed too late to ensure execution of full
sequence of events START, END. So we should to expect so START event
can be not executed (first time).

Author: okbob

src/profiler.c

@@ -3308,7 +3308,12 @@ plpgsql_check_fmgr_hook(FmgrHookEventType event,
 		case FHET_ABORT:
 			stack = (fmgr_hook_private *) DatumGetPointer(*private);
 
-			if (stack->use_plpgsql)
+			/*
+			 * When plpgsql_check is loaded due dependency on some executed function,
+			 * then FHET_START and FHET_END (or FHET_ABORT) can be assymetric. So
+			 * stack can be NULL. See issue #101
+			 */
+			if (stack && stack->use_plpgsql)
 			{
 				profiler_stack *pstack = top_pinfo->prev_pinfo;