PATCH: Fix handling of NUL bytes in zexpandtabs multibyte version

[Mikael Magnusson <mikachu@gmail.com>]

Problem found by dg1727 on #zsh.

---

I checked other uses of zexpandtabs in the same file only and they all
seem to handle the 0 return correctly, and some of them even comment on
it, so fairly confident this is the right fix.

---
 Src/utils.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/Src/utils.c b/Src/utils.c
index 8fcea5362a..f8cbe65ba5 100644
--- a/Src/utils.c
+++ b/Src/utils.c
@@ -5936,8 +5936,11 @@ zexpandtabs(const char *s, int len, int width, int startpos, FILE *fout,
 		memset(&mbs, 0, sizeof(mbs));
 		s++;
 		len--;
-	    } else if (ret == MB_INCOMPLETE) {
+	    } else if (ret == MB_INCOMPLETE ||
 		/* incomplete at end --- assume likewise, best we've got */
+	               ret == 0) {
+		/* NUL character returns 0, which would loop infinitely, so advance
+		 * one byte in this case too */
 		s++;
 		len--;
 	    } else {
-- 
2.15.1