Guard against lone mnemonic prefix at end of key

For --with-lang=am, CppunitTest_sw_dialogs_test hit

> cppunittester: include/rtl/ustring.hxx:764: sal_Unicode rtl::OUString::operator[](sal_Int32) const: Assertion `index >= 0 && static_cast<sal_uInt32>(index) < static_cast<sal_uInt32>(getLength())' failed.

at

> #4  0x00007fffcff543df in rtl::OUString::operator[](int) const (this=0x7ffff3538f40, index=2) at include/rtl/ustring.hxx:764
> #5  0x00007fffd0381b24 in MnemonicGenerator::ImplFindMnemonic(rtl::OUString const&) (this=0x7ffff371c820, rKey="በ_") at vcl/source/window/mnemonic.cxx:67
> #6  0x00007fffd038210c in MnemonicGenerator::RegisterMnemonic(rtl::OUString const&) (this=0x7ffff371c820, rKey="በ_") at vcl/source/window/mnemonic.cxx:89
> #7  0x00007fffb244fa77 in (anonymous namespace)::GtkInstanceBuilder::GenerateMissingMnemonics() (this=0x611000133840) at vcl/unx/gtk3/gtk3gtkinst.cxx:15799
> #8  0x00007fffb2431811 in (anonymous namespace)::GtkInstanceBuilder::GtkInstanceBuilder(_GtkWidget*, rtl::OUString const&, rtl::OUString const&, SystemChildWindow*) (this=0x611000133840, pParent=0x625000260460 [GtkBox], rUIRoot="file:///.../instdir/share/config/soffice.cfg/", rUIFile="modules/swriter/ui/frmtypepage.ui", pInterimGlue=0x0) at vcl/unx/gtk3/gtk3gtkinst.cxx:15784
> #9  0x00007fffb243001a in GtkInstance::CreateBuilder(weld::Widget*, rtl::OUString const&, rtl::OUString const&) (this=0x614000005a40, pParent=0x61700001ef18, rUIRoot="file:///.../instdir/share/config/soffice.cfg/", rUIFile="modules/swriter/ui/frmtypepage.ui") at vcl/unx/gtk3/gtk3gtkinst.cxx:16333
[...]

apparently caused by

> #. ytvmN
> #: sw/uiconfig/swriter/ui/frmtypepage.ui:617
> msgctxt "frmtypepage|horibyft"
> msgid "b_y"
> msgstr "በ_"

in translations/source/am/sw/messages.po

Change-Id: Ie02ed94d159d957984fb3cd91ed6608a6148a570
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/102356
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

0 files changed, 0 insertions, 0 deletions