Fixed bug in key reset on dataXORdWithData selector.

The logic of the changed IF is to handle cases where the data that is being XOR'd (key/data) into the input (self) is of a smaller length. If the length of the key is reached, we reset the pointer to the beginning of the key - repeating the key.

Sample inputs for testing:

Plain Text:
an old man stays at home
3test123

Base 64:
YW4gb2xkIG1hbiBzdGF5cyBhdCBob21l
M3Rlc3QxMjM=

XOR result:
UhpFHBhVEl5SGkUAAFBLQBMVEVMcXl9W

The equivalent is XORing an "old man stays at home" with "3test1233test1233test123"