Fix a bunch of obvious memory leaks at termination

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

src/command/cmd_defs.c

@@ -2882,6 +2882,7 @@ void
 cmd_uninit(void)
 {
     cmd_ac_uninit();
+    g_hash_table_destroy(commands);
     g_hash_table_destroy(search_index);
 }