added test case of having an Empty Map as a Map Value (#81)

* added test case of having an Empty Map as a Map Value

* added test case of having an Empty Map as a Map Value
diff --git a/test/qcbor_decode_tests.h b/test/qcbor_decode_tests.h
index 7e11e35..e6a22f6 100644
--- a/test/qcbor_decode_tests.h
+++ b/test/qcbor_decode_tests.h
@@ -112,6 +112,10 @@
  */
 int32_t ParseMapTest(void);
 
+/*
+  Parses a map that contains a zero-length map as value.
+*/
+int32_t ParseEmptyMapInMapTest(void);
 
 /*
 Test the decoder mode where maps are treated as arrays.