CutLine: return if cliboard read failed

If we ever encounter this clipboard.Read() failure, return false
immediately. Otherwise, InfoBar.Error(err) will have no effect (it will
be immediately overwritten by InfoBar.Message()) so we won't even know
that there was an error.

internal/action/actions.go

@@ -1246,6 +1246,7 @@ func (h *BufPane) CutLine() bool {
 	if h.freshClip && time.Since(h.lastCutTime) < 10*time.Second {
 		if clip, err := clipboard.Read(clipboard.ClipboardReg); err != nil {
 			InfoBar.Error(err)
+			return false
 		} else {
 			clipboard.WriteMulti(clip+string(h.Cursor.GetSelection()), clipboard.ClipboardReg, h.Cursor.Num, h.Buf.NumCursors())
 			totalLines = strings.Count(clip, "\n") + nlines