[StaticAnalyzer] Modernize CFNumberChecker (NFC)

Author: kazutakahirata

clang/lib/StaticAnalyzer/Checkers/BasicObjCFoundationChecks.cpp

@@ -352,9 +352,9 @@ void NilArgChecker::checkPostStmt(const ObjCDictionaryLiteral *DL,
 namespace {
 class CFNumberChecker : public Checker< check::PreStmt<CallExpr> > {
   mutable std::unique_ptr<APIMisuse> BT;
-  mutable IdentifierInfo *ICreate, *IGetValue;
+  mutable IdentifierInfo *ICreate = nullptr, *IGetValue = nullptr;
 public:
-  CFNumberChecker() : ICreate(nullptr), IGetValue(nullptr) {}
+  CFNumberChecker() = default;
 
   void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
 };