Fixes motivated by Coverity #1

As I wrote I fixed a few of the defects coverity found.

There are a lot of uninitialized member/variable defects found by coverity. Most of them are enum values which do not get set when constructing an object. My best guess is that it never made sense to initialize them as no enum value made sense. How should we handle this? Just set their default value to one of the existing possible values or add something like "undefined"? I.e. in src/OSSupport/GZipFile.cpp I set m_Mode to fmRead, but I don't really know at that point if the object is gonna be reading or writing.