Fix panic if no good edge is found in wiperv0.4.1

If findbestedge() found no good edges at all (which is rare but can
happen), then it would panic.

1 files changed, 3 insertions, 0 deletions

diff --git a/wipesides.go b/wipesides.go
index 9183479..b9f5e5c 100644
--- a/wipesides.go
+++ b/wipesides.go
@@ -55,6 +55,9 @@ func findbestedge(img SummableImage, x int, w int) int {
 			bestxs = append(bestxs, x)
 		}
 	}
+	if len(bestxs) == 0 {
+		return 0
+	}
 	middlex := bestxs[len(bestxs)/2]
 
 	return middlex