Merge bitcoin#14783: gui: Fix boost::signals2::no_slots_error in early calls to InitWarning
6bbdb20 squashme: connect thru node interface (João Barbosa)
a0f8df3 qt: Call noui_connect to prevent boost::signals2::no_slots_error in early calls to InitWarning (João Barbosa)
Pull request description:
Adding the following to `bitcoin.conf`
```
[xxx]
disablewallet=1
```
And running `bitcoin-qt` gives:
```
libc++abi.dylib: terminating with uncaught exception of type boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::signals2::no_slots_error> >: boost::signals2::no_slots_error
```
Fixes regression in bitcoin#14708.
---
This is a backport of Core PR14783