Bug with last command feature.

[ArturAssisComp]

The user must type '!!' to execute the last command. The bug arises when the user executes the last command using the history command feature (!!) multiple times in a row, as the following example shows:

$ ls
folder1 folder2 file1
$ !!
Last command: ls
folder1 folder2 file1
$ !!
Last command: !!
Lexical Error: Invalid char '!' at position 0.

To solve this bug, typying '!!' should never call itself as a last command. In the example, it should call 'ls' as the last command in the second time that the user types '!!'.