patch 8.2.2026: Coverity warns for possibly using not NUL terminated string

Problem:    Coverity warns for possibly using not NUL terminated string.
Solution:   Put a NUL in b0_hname just in case.
diff --git a/src/memline.c b/src/memline.c
index bf6a184..19b87d7 100644
--- a/src/memline.c
+++ b/src/memline.c
@@ -2252,6 +2252,7 @@
 
 	mch_get_host_name(hostname, B0_HNAME_SIZE);
 	hostname[B0_HNAME_SIZE - 1] = NUL;
+	b0.b0_hname[B0_HNAME_SIZE - 1] = NUL; // in case of corruption
 	if (STRICMP(b0.b0_hname, hostname) != 0)
 	    ret = FALSE;
     }