block: Use error_abort in bdrv_image_info_specific_dump()

Currently, bdrv_image_info_specific_dump() uses an error variable for
visit_type_ImageInfoSpecific, but ignores the result. As this function
is used here with an output visitor to transform the ImageInfoSpecific
object to a generic QDict, an error should actually be impossible. It is
however better to assert that this is indeed the case. This is done by
this patch using error_abort instead of an unused local Error variable.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Reported-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/qapi.c

@@ -532,12 +532,11 @@ static void dump_qdict(fprintf_function func_fprintf, void *f, int indentation,
 void bdrv_image_info_specific_dump(fprintf_function func_fprintf, void *f,
                                    ImageInfoSpecific *info_spec)
 {
-    Error *local_err = NULL;
     QmpOutputVisitor *ov = qmp_output_visitor_new();
     QObject *obj, *data;
 
     visit_type_ImageInfoSpecific(qmp_output_get_visitor(ov), &info_spec, NULL,
-                                 &local_err);
+                                 &error_abort);
     obj = qmp_output_get_qobject(ov);
     assert(qobject_type(obj) == QTYPE_QDICT);
     data = qdict_get(qobject_to_qdict(obj), "data");