tdf#39440: fix several warnings reported by cppcheck

Change-Id: I560d28b7cc67740c6479494d0e5aa62d2ac6ffae
Reviewed-on: https://gerrit.libreoffice.org/19587
Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Thorsten Behrens <Thorsten.Behrens@CIB.de>

compilerplugins/clang/staticmethods.cxx

@@ -21,7 +21,7 @@ class StaticMethods:
 private:
     bool bVisitedThis;
 public:
-    explicit StaticMethods(InstantiationData const & data): Plugin(data) {}
+    explicit StaticMethods(InstantiationData const & data): Plugin(data), bVisitedThis(false) {}
 
     void run() override
     { TraverseDecl(compiler.getASTContext().getTranslationUnitDecl()); }