routing/blindedpath: dont error out unless all paths fail

In this commit, we adjust BuildBlindedPaymentPaths to only error out
completely if none of the paths it received from FindRoutes resulted in
a usable blinded path.

routing/blindedpath/blinded_path.go

@@ -141,10 +141,11 @@ func BuildBlindedPaymentPaths(cfg *BuildBlindedPathCfg) (
 				route)
 
 			continue
-		}
+		} else if err != nil {
+			log.Errorf("Not using route (%s) as a blinded path: %v",
+				err)
 
-		if err != nil {
-			return nil, err
+			continue
 		}
 
 		paths = append(paths, path)