De-referencing c++ iterator without null check may be unsafe

\qt3d\src\render\materialsystem\shadercache.cpp

L79～
===
auto it = std::lower_bound(programRefs.begin(), programRefs.end(),
shaderPeerId);

if (*it != shaderPeerId)

programRefs.insert(it, shaderPeerId);
===

it is possible that "it" will get value programRefs.end(), and according to c++ document dereferencing iterator to end()  will have undefined behavior