[gexiv2] Fix throwing error with >= 0.27

[Jens Georg <jensgeorg src gnome org>]

commit e2a08d551f653cf49c40e0974544c436a92d4b50
Author: Jens Georg <mail jensge org>
Date:   Wed Jan 2 11:00:06 2019 +0100

    Fix throwing error with >= 0.27
    
    Fixes #36

 gexiv2/gexiv2-metadata.cpp | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/gexiv2/gexiv2-metadata.cpp b/gexiv2/gexiv2-metadata.cpp
index bb8a50f..a3257ee 100644
--- a/gexiv2/gexiv2-metadata.cpp
+++ b/gexiv2/gexiv2-metadata.cpp
@@ -84,7 +84,11 @@ public:
             g_clear_error (&_error);
             _error = error;
 
+#if EXIV2_TEST_VERSION(0,27,0)
+            throw Exiv2::Error(Exiv2::ErrorCode::kerFailedToReadImageData);
+#else
             throw Exiv2::Error(2);
+#endif
             return 0;
         }