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/journal/catalog.c b/src/journal/catalog.c
index e505a05305..0801e13599 100644
--- a/src/journal/catalog.c
+++ b/src/journal/catalog.c
@@ -558,7 +558,7 @@ static const char *find_id(void *p, sd_id128_t id) {
 int catalog_get(const char* database, sd_id128_t id, char **_text) {
         _cleanup_close_ int fd = -1;
         void *p = NULL;
-        struct stat st;
+        struct stat st = {};
         char *text = NULL;
         int r;
         const char *s;