clang-tidy: use nullptr

Signed-off-by: Rosen Penev <rosenp@gmail.com>

src/tiffcomposite_int.hpp

@@ -1547,7 +1547,7 @@ TiffComponent::UniquePtr newTiffBinaryArray0(uint16_t tag, IfdId group) {
 //! Function to create and initialize a new simple binary array entry
 template <const ArrayCfg* arrayCfg>
 TiffComponent::UniquePtr newTiffBinaryArray1(uint16_t tag, IfdId group) {
-  return TiffComponent::UniquePtr(new TiffBinaryArray(tag, group, arrayCfg, 0, 0));
+  return TiffComponent::UniquePtr(new TiffBinaryArray(tag, group, arrayCfg, nullptr, 0));
 }
 
 //! Function to create and initialize a new complex binary array entry

src/xmp.cpp

@@ -68,7 +68,7 @@ class XMLValidator {
  private:
   // Private constructor, because this class is only constructed by
   // the (static) check method.
-  XMLValidator() : parser_(XML_ParserCreateNS(0, '@')) {
+  XMLValidator() : parser_(XML_ParserCreateNS(nullptr, '@')) {
     if (!parser_) {
       throw Error(ErrorCode::kerXMPToolkitError, "Could not create expat parser");
     }