[PATCH v2 1/2] settings: Fix uninitialised use

__attribute__(cleanup) variables need to be initialised in situ.

In file included from ell/private.h:8,
                 from ell/settings.c:36:
In function 'auto_free',
    inlined from 'l_settings_set_double' at ell/settings.c:1335:2:
./ell/util.h:265:9: warning: 'buf' may be used uninitialized [-Wmaybe-uninitialized]
  265 |         l_free(*p);
      |         ^~~~~~~~~~
ell/settings.c: In function 'l_settings_set_double':
ell/settings.c:1335:33: note: 'buf' was declared here
 1335 |         L_AUTO_FREE_VAR(char *, buf);
      |                                 ^~~
In function 'auto_free',
    inlined from 'l_settings_set_float' at ell/settings.c:1381:2:
./ell/util.h:265:9: warning: 'buf' may be used uninitialized [-Wmaybe-uninitialized]
  265 |         l_free(*p);
      |         ^~~~~~~~~~
ell/settings.c: In function 'l_settings_set_float':
ell/settings.c:1381:33: note: 'buf' was declared here
 1381 |         L_AUTO_FREE_VAR(char *, buf);
      |                                 ^~~
---
Changes since v1:
- Fix the fix to note create more warnings

 ell/settings.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/ell/settings.c b/ell/settings.c
index b46d00bd2899..01307ba72b87 100644
--- a/ell/settings.c
+++ b/ell/settings.c
@@ -1332,7 +1332,7 @@ LIB_EXPORT bool l_settings_set_double(struct l_settings *settings,
 					const char *group_name, const char *key,
 					double in)
 {
-	L_AUTO_FREE_VAR(char *, buf);
+	L_AUTO_FREE_VAR(char *, buf) = NULL;
 
 	buf = l_strdup_printf("%f", in);
 
@@ -1378,7 +1378,7 @@ LIB_EXPORT bool l_settings_set_float(struct l_settings *settings,
 					const char *group_name, const char *key,
 					float in)
 {
-	L_AUTO_FREE_VAR(char *, buf);
+	L_AUTO_FREE_VAR(char *, buf) = NULL;
 
 	buf = l_strdup_printf("%f", (double)in);
 
-- 
2.55.0