[mythtv-cmyth] Zero buffer in MythEventHandlerPrivate::SetRecordingEventListener

Conditional jump or move depends on uninitialised value(s)
  at 0x4C2D7A9: strlen (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
  by 0x589B5FB: std::string::assign(char const*) (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.17)
  by 0x40EBE7: void ssasn<char>(std::basic_string<char, std::char_traits<char>, std::allocator<char> >&, char const*) (StdString.h:1300)
  by 0x50562B: MythEventHandler::MythEventHandlerPrivate::SetRecordingEventListener(CStdStr<char> const&, MythFile const&) (StdString.h:2179)
  by 0x5056FB: MythEventHandler::SetRecordingListener(CStdStr<char> const&, MythFile const&) (MythEventHandler.cpp:585)
  by 0x4DA944: PVRClientMythTV::OpenRecordedStream(PVR_RECORDING const&) (pvrclient-mythtv.cpp:1718)
...
Uninitialised value was created by a stack allocation
  at 0x5055C0: MythEventHandler::MythEventHandlerPrivate::SetRecordingEventListener(CStdStr<char> const&, MythFile const&) (MythEventHandler.cpp:362)