Update Ubuntu VM to 18.04 and remove external kubuntu backports PPA
previously used to get Qt packages.
While we're at it, remove libglu1-mesa-dev package too. The external
repo for libunarr is still needed as Ubuntu 18.04 does not package
it yet (it is included in 20.04)
Before this commit starting a search when an empty folder or an empty
reading list was selected left all comics actions disabled. Fixes#213.
When search mode is exited, we always call either
YACReaderNavigationController::loadFolderInfo() or
YACReaderNavigationController::loadListInfo(). Both of them call
LibraryWindow::disableComicsActions(), so the enabled/disabled state of
the comics actions stays up-to-date at all times.
Currently these objects are created once at program startup and are
never destroyed. Printing debug messages in the models' destructors
confirms the leaks and proves that with this fix the objects are
destroyed at Library exit.
Qmake by default creates lots of unnecessary information during builds
which makes it hard to extract warnings and errors from the log.
Add the undocumented silent parameter to make it less talky.
InfoComicsView constructor is the only function that connects to
FlowView's currentCoverChanged signal. Neither of the slots connected to
this signal handles the argument value index==-1. So when FlowView emits
this signal with index==-1, YACReaderLibrary crashes. Returning early
from either ComicsView::updateInfoForIndex() or
InfoComicsView::setCurrentIndex() when index==-1 is not sufficient - the
crash happens in the other slot then. Let us skip emitting the signal in
FlowView if index==-1 rather than return early from both slots.
Steps to reproduce 1:
1. Launch YACReaderLibrary version that matches the version of the
default library database. Alternatively, select a compatible library
after starting the application.
2. If InfoComicsView is not active, switch to it.
3. (optional) Switch to another comics view out of InfoComicsView.
4. Quit YACReaderLibrary. The application crashes during exit - after
the "YACReaderLibrary closed with exit code : 0" message is printed.
Steps to reproduce 2:
1. Launch a YACReaderLibrary version newer than the version of the
default library database.
2. Click the "No" button in the "Update needed" dialog that pops up.
3. Change between comics views until InfoComicsView becomes active. If
this view was active at the beginning, switch through all the views to
get back to it. At this point YACReaderLibrary crashes.
