Update guiutil.cpp

It's the one place in the codebase where a change in the string length can interfere with the program semantics.
In the [bitcoin codebase](https://github.com/bitcoin/bitcoin/blob/master/src/qt/guiutil.cpp#L190) the length for "bitcoin://" is correctly bound to 10. Fractalcoin's binding of 11 is incorrect. For "bitchcoin://" the integer parameter should be bound to 12:
```#!python
>>> len('bitchcoin://')
12
```