Fix raw loggin use of uninitialized value introduced in previous commit

src/logging.c

@@ -446,7 +446,7 @@ static inline void uc_vlog_file(const struct UCLogArgs *args, time_t tstamp, con
     struct UCLogDestination *dest = args->dest;
     char time_buf[48];
     struct tm t;
-    int rc;
+    int rc = 0;
 
     if (dest->type.file.file == NULL)
         return;