gitk: Fix bug in the anc_or_desc routine

I missed the case where both nodes have no children and therefore
have no incoming arcs.  This fixes it.

Signed-off-by: Paul Mackerras <paulus@samba.org>

diff --git a/gitk b/gitk
index d509145..767b0ed 100755 (executable)
--- a/gitk
+++ b/gitk
@@ -6261,7 +6261,8 @@ proc anc_or_desc {a b} {
        # Both are on the same arc(s); either both are the same BMP,
        # or if one is not a BMP, the other is also not a BMP or is
        # the BMP at end of the arc (and it only has 1 incoming arc).
-       if {$a eq $b} {
+       # Or both can be BMPs with no incoming arcs.
+       if {$a eq $b || $arcnos($a) eq {}} {
            return 0
        }
        # assert {[llength $arcnos($a)] == 1}