fix an obvious bug found by clang++ and collapse a redundant if.

Here's the diagnostic from clang:

/Volumes/Data/dgregor/Projects/llvm/lib/Target/CppBackend/CPPBackend.cpp:989:23: warning: 'gv' is always NULL in this context
        printConstant(gv);
                      ^
1 diagnostic generated.

llvm-svn: 91318