FIX(client): Crash when opening connect dialog

When selecting new public servers, we randomize their order. The random
number used for that is an unsigned integer from which we compute the
modulus with the list size in order to get a random index into the list.

This involved an implicit conversion from an unsigned integer (the
random number) to a signed integer (the list index - as Qt uses signed
integers for that). Thus, b5a67c0 added
an explicit cast to a signed integer. However, it did this to the random
number before the modulus operation, meaning that if a large enough
random number is drawn, the cast would actually create a negative
integer, yielding a negative list index after the modulus. This caused a
crash of the application.

The fix consists in switching to using the bounded() function that has
an overload for signed integers and which can directly generate numbers
in the desired range, making all of the above superfluous.

Fixes #6306

Co-authored-by: Thomas Lange <[email protected]>

src/mumble/ConnectDialog.cpp

@@ -41,9 +41,7 @@
 #	include <shlobj.h>
 #endif
 
-#if QT_VERSION >= QT_VERSION_CHECK(5, 10, 0)
-#	include <QRandomGenerator>
-#endif
+#include <QRandomGenerator>
 
 #include <algorithm>
 
@@ -1466,13 +1464,7 @@ void ConnectDialog::fillList() {
 	}
 
 	while (!ql.isEmpty()) {
-#if QT_VERSION >= QT_VERSION_CHECK(5, 10, 0)
-		ServerItem *si = static_cast< ServerItem * >(
-			ql.takeAt(static_cast< int >(QRandomGenerator::global()->generate()) % ql.count()));
-#else
-		// Qt 5.10 introduces the QRandomGenerator class and in Qt 5.15 qrand got deprecated in its favor
-		ServerItem *si = static_cast< ServerItem * >(ql.takeAt(qrand() % ql.count()));
-#endif
+		ServerItem *si = static_cast< ServerItem * >(ql.takeAt(QRandomGenerator::global()->bounded(0, ql.count())));
 		qlNew << si;
 		qlItems << si;
 	}