Fix illustration.

`Book::getIllustration(size)` return a `shared_ptr<Illustration>`.
The current `buildWrapper` was creating a wrapper on a
`shared_ptr<Illustration>` (so a `shared_ptr<shared_ptr<Illustration>>`)
but we was converting to a `shared_ptr<Illustration>` and so we were doing
wrong reads.

By specializing the buildWrapper for `shared_ptr<T>`, we avoid the
"double shared_ptr" and we are good.

lib/src/main/cpp/libkiwix/illustration.cpp

@@ -19,7 +19,7 @@
 
 
 #include <jni.h>
-#include "org_kiwix_libkiwix_Book.h"
+#include "org_kiwix_libkiwix_Illustration.h"
 
 #include "utils.h"
 #include "book.h"

lib/src/main/cpp/utils.h

@@ -141,6 +141,14 @@ inline jobject buildWrapper(JNIEnv* env, const char* class_name, T&& obj, const
   setPtr(env, wrapper, std::move(ptr));
   return wrapper;
 }
+
+template<typename T>
+inline jobject buildWrapper(JNIEnv* env, const char* class_name, std::shared_ptr<T>&& ptr, const char* handleName = "nativeHandle") {
+  auto wrapper = newObject(class_name, env);
+  setPtr(env, wrapper, std::move(ptr));
+  return wrapper;
+}
+
 #define BUILD_WRAPPER(CLASSNAME, OBJ) buildWrapper(env, CLASSNAME, std::move(OBJ))
 
 template<typename T>

lib/src/test/test.java

@@ -122,6 +122,7 @@ public class test {
         Book book = lib.getBookById(bookIds[0]);
         assertEquals(book.getTitle(), "Test ZIM file");
         assertEquals(book.getTags(), "unit;test");
+        assertEquals(book.getIllustration(48).width(), 48);
         assertEquals(book.getIllustration(48).url(), "http://localhost/meta?name=favicon&content=small");
         assertEquals(book.getUrl(), "http://localhost/small.zim");