[9.x] db:table command properly handle table who doesn't exist

[kichetof]

New db:table doesn't proper handle table who doesn't exist.

When I first tried it, I run artisan db:table user (forgot the s) and instead of getting an error message I got an error:

   ErrorException 

  Attempt to read property "size" on null

  at vendor/laravel/framework/src/Illuminate/Database/Console/DatabaseInspectionCommand.php:89
     85▕     {
     86▕         return $connection->selectOne('SELECT (data_length + index_length) AS size FROM information_schema.TABLES WHERE table_schema = ? AND table_name = ?', [
     87▕             $connection->getDatabaseName(),
     88▕             $table,
  ➜  89▕         ])->size;
     90▕     }
     91▕ 
     92▕     /**
     93▕      * Get the size of a Postgres table in bytes.

      +16 vendor frames 
  17  artisan:37
      Illuminate\Foundation\Console\Kernel::handle()

This PR fix it by checking if table exists before accessing any properties.