QDict: Rename 'err_value'

A missing key is not an error.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
diff --git a/qdict.h b/qdict.h
index 5e5902c..72ea563 100644
--- a/qdict.h
+++ b/qdict.h
@@ -56,7 +56,7 @@
 QDict *qdict_get_qdict(const QDict *qdict, const char *key);
 const char *qdict_get_str(const QDict *qdict, const char *key);
 int64_t qdict_get_try_int(const QDict *qdict, const char *key,
-                          int64_t err_value);
+                          int64_t def_value);
 const char *qdict_get_try_str(const QDict *qdict, const char *key);
 
 #endif /* QDICT_H */