C++: Fix uninitialized value warnings

...from coverity scan.

Change-Id: I44663354b3ee4854dd6335121a0160e35f14976c
Reviewed-by: Robert Loehning <robert.loehning@qt.io>

src/libs/cplusplus/ResolveExpression.cpp

@@ -192,7 +192,7 @@ private:
 
     const LookupContext &_context;
     // binding has to be remembered in case of resolving typedefs for templates
-    ClassOrNamespace *_binding;
+    ClassOrNamespace *_binding = nullptr;
 };
 
 static int evaluateFunctionArgument(const FullySpecifiedType &actualTy,