I saw this message:
```
lightning_channeld: outstanding taken(): channeld/channeld.c:3087:blinding
lightning_channeld: outstanding taken(): channeld/channeld.c:3087:blinding
lightning_channeld: outstanding taken(): channeld/channeld.c:3087:blinding
```
The caller does take(blinding), but blinding can be NULL. We should
move the code around to do the take() earlier anyway.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>