runtime/docker/node: logreader must not be nil

Check for nil when trying to return exec process log reader.
Fixes #377

pkg/cluster/host.go

@@ -78,6 +78,13 @@ func resolveHostnameFromInside(ctx context.Context, rtime rt.Runtime, node *k3d.
 
 	logreader, execErr := rtime.ExecInNodeGetLogs(ctx, node, []string{"sh", "-c", fmt.Sprintf("nslookup %s", hostname)})
 
+	if logreader == nil {
+		if execErr != nil {
+			return nil, execErr
+		}
+		return nil, fmt.Errorf("Failed to get logs from exec process")
+	}
+
 	submatches := map[string]string{}
 	scanner := bufio.NewScanner(logreader)
 	if scanner == nil {

pkg/runtimes/docker/node.go

@@ -308,7 +308,10 @@ func (d Docker) GetNodeLogs(ctx context.Context, node *k3d.Node, since time.Time
 func (d Docker) ExecInNodeGetLogs(ctx context.Context, node *k3d.Node, cmd []string) (*bufio.Reader, error) {
 	resp, err := executeInNode(ctx, node, cmd)
 	if err != nil {
-		return resp.Reader, err
+		if resp.Reader != nil { // sometimes the exec process returns with a non-zero exit code, but we still have the logs we
+			return resp.Reader, err
+		}
+		return nil, err
 	}
 	return resp.Reader, nil
 }