Crash on dlclose when toUtf8 is used in dynamic library

I have an application that is started as a plugin. The plugin is loaded with dlopen(). Loading, running and closing the plugin is all done in the main() thread. When the loaded library is closed with dlclose(), ~QFactoryLoader generates a SIGSEGV.
The crash only happens if QString::toUtf8() is used in the dynamic library (does not have to be run, just symbols used).

Steps to reproduce:

1. Create a non-qt application (MAIN)
2. Create a module using QtCore that uses the QString::toUtf8 symbol and starts a QApplication (MODULE).
3. From MAIN, load MODULE with dlopen().
4. From MAIN, execute some code in MODULE (via dlsym) that starts a QApplication and quits QApplication (with a QTimer for example).
5. Unload MODULE with dlclose().
6. Program segfaults in QFactoryLoader::~QFactoryLoader

The bug is not present when using 4.7.45 but present in 4.8.0.

I have attached a code sample that demonstrates this bug. Build and run it with:

$ tar xzf qtbug.tgz
$ cd qtbug
$ make
Qt BUG related to dlclose
=========================
1. Program starting.
2. Loading dynamic library 'mod.so' linked to Qt.
3. Getting 'run_test' function.
4. Passing control to Qt.
[in mod] Qt lib version: 4.8.0.
5. 'mod' returned.
6. Calling dlclose.
make[3]: *** [CMakeFiles/test] Segmentation fault

Backtrace

Program received signal SIGSEGV, Segmentation fault.
0x00f6ee6e in ?? () from /home/gaspard/QtSDK/Desktop/Qt/4.8.0/gcc/lib/libQtCore.so.4
(gdb) bt
#0 0x00f6ee6e in ?? ()
from /home/gaspard/QtSDK/Desktop/Qt/4.8.0/gcc/lib/libQtCore.so.4
#1 0x00f6b0e2 in QFactoryLoader::~QFactoryLoader() ()
from /home/gaspard/QtSDK/Desktop/Qt/4.8.0/gcc/lib/libQtCore.so.4
#2 0x0050978a in ?? ()
from /home/gaspard/QtSDK/Desktop/Qt/4.8.0/gcc/lib/libQtGui.so.4
#3 0x00183d2b in __cxa_finalize () from /lib/i386-linux-gnu/libc.so.6
#4 0x0042c304 in ?? ()
from /home/gaspard/QtSDK/Desktop/Qt/4.8.0/gcc/lib/libQtGui.so.4
#5 0x00bcf850 in _fini ()
from /home/gaspard/QtSDK/Desktop/Qt/4.8.0/gcc/lib/libQtGui.so.4
#6 0x00123145 in ?? () from /lib/ld-linux.so.2
#7 0x00123b98 in ?? () from /lib/ld-linux.so.2
#8 0x00131cf2 in ?? () from /lib/i386-linux-gnu/libdl.so.2
#9 0x0011e61f in ?? () from /lib/ld-linux.so.2
#10 0x0013233a in ?? () from /lib/i386-linux-gnu/libdl.so.2
#11 0x00131d28 in dlclose () from /lib/i386-linux-gnu/libdl.so.2
#12 0x080487f8 in main ()