dgit: Avoid crash if branch_is_gdr finds an origin commit

Closes: #910687.
Reported-by: Mattia Rizzolo <mattia@debian.org>
Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>

1 files changed, 4 insertions, 0 deletions

diff --git a/dgit b/dgit
index 4cc5684..19b9eb2 100755
--- a/dgit
+++ b/dgit
@@ -379,6 +379,10 @@ sub branch_is_gdr ($) {
 	    printdebug "branch_is_gdr  $walk ?-octopus NO\n";
 	    return 0;
 	}
+	if (!@parents) {
+	    printdebug "branch_is_gdr  $walk origin\n";
+	    return 0;
+	}
 	if ($get_patches->($walk) ne $tip_patches) {
 	    # Our parent added, removed, or edited patches, and wasn't
 	    # a gdr make-patches commit.  gdr make-patches probably