bug: Fix crash when calling ImageFactory::create(none)

include/exiv2/types.hpp

@@ -486,7 +486,7 @@ namespace Exiv2 {
     const T* find(T (&src)[N], const K& key)
     {
         const T* rc = std::find(src, src + N, key);
-        return rc == src + N ? 0 : rc;
+        return rc == src + N ? nullptr : rc;
     }
 
     //! Template used in the COUNTOF macro to determine the size of an array

src/image.cpp

@@ -920,10 +920,12 @@ namespace Exiv2 {
     {
         // BasicIo instance does not need to be open
         const Registry* r = find(registry, type);
-        if (nullptr != r) {
-            return r->newInstance_(std::move(io), true);
+
+        if (r == nullptr || type == ImageType::none) {
+            return Image::UniquePtr();
         }
-        return nullptr;
+
+        return r->newInstance_(std::move(io), true);
     }
 
 // *****************************************************************************

unitTests/test_ImageFactory.cpp

@@ -42,6 +42,11 @@ TEST(TheImageFactory, cannotCreateInstancesForSomeTypesInMemory)
     EXPECT_THROW(ImageFactory::create(ImageType::srw), Error);
 }
 
+TEST(TheImageFactory, throwsWithImageTypeNone)
+{
+    EXPECT_THROW(ImageFactory::create(ImageType::none), Error);
+}
+
 TEST(TheImageFactory, throwsWithNonExistingImageTypes)
 {
     EXPECT_THROW(ImageFactory::create(static_cast<ImageType>(666)), Error);