fix bug in TRE found by clang (typo && instead of &)

src/regex/regexec.c

@@ -917,7 +917,7 @@ tre_tnfa_run_backtrack(const tre_tnfa_t *tnfa, const void *string,
 	  if (stack->prev)
 	    {
 	      DPRINT(("	 backtracking\n"));
-	      if (stack->item.state->assertions && ASSERT_BACKREF)
+	      if (stack->item.state->assertions & ASSERT_BACKREF)
 		{
 		  DPRINT(("  states_seen[%d] = 0\n",
 			  stack->item.state_id));