The code is a bit too complex for gcc to track it:
```
In file included from ccan/ccan/tal/str/str.h:7,
from plugins/askrene/askrene.c:11:
plugins/askrene/askrene.c: In function ‘do_getroutes’:
ccan/ccan/tal/tal.h:324:23: error: ‘routes’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
324 | #define tal_count(p) (tal_bytelen(p) / sizeof(*p))
| ^~~~~~~~~~~
plugins/askrene/askrene.c:476:24: note: ‘routes’ was declared here
476 | struct route **routes;
| ^~~~~~
plugins/askrene/askrene.c:475:29: error: ‘amounts’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
475 | struct amount_msat *amounts;
| ^~~~~~~
plugins/askrene/askrene.c:488:69: error: ‘probability’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
488 | json_add_u64(response, "probability_ppm", (u64)(probability * 1000000));
| ~~~~~~~~~~~~~^~~~~~~~~~
cc plugins/askrene/dijkstra.c
cc1: all warnings being treated as errors
```
On my local machine, it also warns in param_dev_channel, so I fixed that too.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
e3c9bc6d3a