fix gcc warnings about uninitialized variables

like:

src/shared/install.c: In function ‘unit_file_lookup_state’:
src/shared/install.c:1861:16: warning: ‘r’ may be used uninitialized in
this function [-Wmaybe-uninitialized]
         return r < 0 ? r : state;
                ^
src/shared/install.c:1796:13: note: ‘r’ was declared here
         int r;
             ^

1 files changed, 1 insertions, 1 deletions

diff --git a/src/libsystemd-network/sd-pppoe.c b/src/libsystemd-network/sd-pppoe.c
index e8e7d994df..601f3bd400 100644
--- a/src/libsystemd-network/sd-pppoe.c
+++ b/src/libsystemd-network/sd-pppoe.c
@@ -339,7 +339,7 @@ static int pppoe_timeout(sd_event_source *s, uint64_t usec, void *userdata);
 
 static int pppoe_arm_timeout(sd_pppoe *ppp) {
         _cleanup_event_source_unref_ sd_event_source *timeout = NULL;
-        usec_t next_timeout;
+        usec_t next_timeout = 0;
         int r;
 
         assert(ppp);