Fix for bug #54253: memory leak when using I_S plugins w/o deinit method

Free memory allocated by the server for all plugins,
with or without deinit() method.

sql/sql_show.cc

@@ -6930,13 +6930,16 @@ int finalize_schema_table(st_plugin_int *plugin)
   ST_SCHEMA_TABLE *schema_table= (ST_SCHEMA_TABLE *)plugin->data;
   DBUG_ENTER("finalize_schema_table");
 
-  if (schema_table && plugin->plugin->deinit)
+  if (schema_table)
   {
-    DBUG_PRINT("info", ("Deinitializing plugin: '%s'", plugin->name.str));
-    if (plugin->plugin->deinit(NULL))
+    if (plugin->plugin->deinit)
     {
-      DBUG_PRINT("warning", ("Plugin '%s' deinit function returned error.",
-                             plugin->name.str));
+      DBUG_PRINT("info", ("Deinitializing plugin: '%s'", plugin->name.str));
+      if (plugin->plugin->deinit(NULL))
+      {
+        DBUG_PRINT("warning", ("Plugin '%s' deinit function returned error.",
+                               plugin->name.str));
+      }
     }
     my_free(schema_table, MYF(0));
   }