feature/fix-the-long-lines-display-bug 9de00e5fda: Avoid assertion violations in 'back_to_previous_visible_line_start'

[Eli Zaretskii]

branch: feature/fix-the-long-lines-display-bug
commit 9de00e5fda2e04316357bd8cf0d8094c63ff171b
Author: Eli Zaretskii <eliz@gnu.org>
Commit: Eli Zaretskii <eliz@gnu.org>

    Avoid assertion violations in 'back_to_previous_visible_line_start'
    
    * src/xdisp.c (back_to_previous_visible_line_start): Avoid
    assertion violations when narrowed_begv is in effect.
---
 src/xdisp.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/xdisp.c b/src/xdisp.c
index 84203f0ed0..ac76917eb3 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -7226,7 +7226,8 @@ back_to_previous_visible_line_start (struct it *it)
   it->continuation_lines_width = 0;
 
   eassert (IT_CHARPOS (*it) >= BEGV);
-  eassert (IT_CHARPOS (*it) == BEGV
+  eassert (it->narrowed_begv > BEGV
+          || IT_CHARPOS (*it) == BEGV
           || FETCH_BYTE (IT_BYTEPOS (*it) - 1) == '\n');
   CHECK_IT (it);
 }