Git: Initialize some member variables in constructor

Detected by CppCheck

Change-Id: I4dfafc75349a6f14e050cbf405f0b2dc9fce5cef
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/git/gerrit/gerritplugin.cpp

@@ -266,6 +266,7 @@ void FetchContext::checkout()
 GerritPlugin::GerritPlugin(QObject *parent)
     : QObject(parent)
     , m_parameters(new GerritParameters)
+    , m_gerritCommand(0), m_pushToGerritCommand(0)
 {
 }