patch 8.2.4951: smart indenting done when not enabled

Problem:    Smart indenting done when not enabled.
Solution:   Check option values before setting can_si. (closes #10420)
diff --git a/src/ops.c b/src/ops.c
index 4adeb09..b11cbf5 100644
--- a/src/ops.c
+++ b/src/ops.c
@@ -1718,12 +1718,7 @@
     {
 	l = 0;
 #ifdef FEAT_SMARTINDENT
-	if (!p_paste && curbuf->b_p_si
-# ifdef FEAT_CINDENT
-		&& !curbuf->b_p_cin
-# endif
-		)
-	    can_si = TRUE;	// It's like opening a new line, do si
+	can_si = may_do_si();	// Like opening a new line, do smart indent
 #endif
     }