This crash is not always reproducible but occurs ofter.

0) Start kmail-mobile
1) Select a folder
2) Click on folder to get into multiselection view
3) Select >2 mails
4) Copy mails to another folder

(gdb) bt full
#0  QSortFilterProxyModelPrivate::proxy_to_source (this=0x2e4db0, proxy_index=...) at itemviews/qsortfilterproxymodel.cpp:368
        m = <value optimized out>
        source_row = <value optimized out>
        source_col = <value optimized out>
#1  0x41b6f078 in QSortFilterProxyModel::mapToSource (this=<value optimized out>, proxyIndex=...) at itemviews/qsortfilterproxymodel.cpp:2491
No locals.
#2  0x41b6e1b0 in QSortFilterProxyModelPrivate::store_persistent_indexes (this=<value optimized out>) at itemviews/qsortfilterproxymodel.cpp:994
        proxy_index = {r = 2, c = 0, p = 0xa1e728, m = 0x2e4998}
        source_index = {r = 7, c = 304304, p = 0x2e5fc0, m = 0x0}
        data = <value optimized out>
        _container_ = {c = {{d = 0x95a220, e = 0x95a220}}, brk = 11259104, i = {i = 0x0}, e = {i = 0x1028}}
        source_indexes = @0xbead478c
        q = 0x2e4998
#3  0x41b6e4ac in QSortFilterProxyModelPrivate::_q_sourceLayoutAboutToBeChanged (this=0x2e4db0) at itemviews/qsortfilterproxymodel.cpp:1242
        q = 0x2e4998
#4  0x41b79080 in QSortFilterProxyModel::qt_metacall (this=0x2e4998, _c=QMetaObject::InvokeMetaMethod, _id=9, _a=0xbead487c) at .moc/release-shared/moc_qsortfilterproxymodel.cpp:132
No locals.
#5  0x405991d8 in Akonadi::EntityMimeTypeFilterModel::qt_metacall(QMetaObject::Call, int, void**) () from /usr/lib/libakonadi-kde.so.4
No symbol table info available.
#6  0x423cdbf4 in QMetaObject::metacall (object=0xbead472c, cl=3034544, idx=-1095940292, argv=0xa1e728) at kernel/qmetaobject.cpp:237
        mo = <value optimized out>
#7  0x423e4b98 in QMetaObject::activate (sender=0x2e20f8, m=<value optimized out>, local_signal_index=<value optimized out>, argv=0xa1e728) at kernel/qobject.cpp:3272
        receiverInSameThread = true
        previousSender = 0x0
        method = 34
        currentSender = {sender = 0x2e20f8, signal = 7, ref = 1}
        c = 0x2e5010
        last = 0x2e5010
        signalOffset = <value optimized out>
        methodOffset = <value optimized out>
        signal_index = 5
        signal_absolute_index = 7
        empty_argv = {0x0}
        currentThreadData = 0x4a4b0
        connectionLists = 0x2e2110
#8  0x4244e498 in QAbstractItemModel::layoutAboutToBeChanged (this=0xbead472c) at .moc/release-shared/moc_qabstractitemmodel.cpp:167
No locals.
#9  0x4118c9ac in ?? () from /usr/lib/libkdeui.so.5
No symbol table info available.
#10 0x4118c9ac in ?? () from /usr/lib/libkdeui.so.5
No symbol table info available.
Backtrace stopped: previous frame identical to this frame (corrupt stack?)