Add missing ENOMEM check

Signed-off-by: Kevin Svetlitski <[email protected]>

libdrgn/program.c

@@ -666,6 +666,8 @@ struct drgn_error *drgn_program_cache_thread(struct drgn_program *prog,
         if (err)
             return err;
         struct drgn_thread *thread = malloc(sizeof(struct drgn_thread));
+		if (!thread)
+			return &drgn_enomem;
         *thread = (struct drgn_thread){ .tid = entry.key, .prstatus = { data, size } };
         if (drgn_thread_map_size(&prog->thread_map) == 0) {
             // Having perused the GDB, BFD, and Kernel source code, it appears that