What reason does Crooks first give for Lennie not being welcome in Crook's room ?

Crooks notes that he isn't welcome in the bunkhouse, therefore, no one is welcome in his room.

Crooks said sharply, "You got no right to come in my room. This here’s my room. Nobody got any right in here but me."

Lennie gulped and his smile grew more fawning. "I ain’t doing nothing," he said. "Just come to look at my puppy. And I seen your light," he explained.

"Well, I got a right to have a light. You go on get outa my room. I ain’t wanted in the bunk house, and you ain’t wanted in my room."