tests: Make the static ananlyzers happy with the threads

Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Norbert Pocs <norbertpocs0@gmail.com>

tests/unittests/torture_threads_buffer.c

@@ -119,6 +119,8 @@ static void *thread_growing_buffer_shifting(void *threadid)
     buffer = ssh_buffer_new();
     if (buffer == NULL) {
         pthread_exit((void *)-1);
+        /* dummy analyzers ... */
+        return NULL;
     }
     ssh_buffer_set_secure(buffer);