make for loop more clear in logger watcher

This wasn't a bug, but add -1 here makes it more clear. The function will
early exit in any cases where it would've overflowed here.

thanks to shqking on github for the report

1 files changed, 1 insertions, 1 deletions

diff --git a/logger.c b/logger.c
index 25105ab..fdc2c19 100644
--- a/logger.c
+++ b/logger.c
@@ -721,7 +721,7 @@ enum logger_add_watcher_ret logger_add_watcher(void *c, const int sfd, uint16_t
         return LOGGER_ADD_WATCHER_TOO_MANY;
     }
 
-    for (x = 0; x < WATCHER_LIMIT; x++) {
+    for (x = 0; x < WATCHER_LIMIT-1; x++) {
         if (watchers[x] == NULL)
             break;
     }