added missing test for methods

tests/method/tnildispatcher.nim

@@ -0,0 +1,21 @@
+discard """
+  outputsub: '''Error: unhandled exception: cannot dispatch; dispatcher is nil [NilAccessError]'''
+  exitcode: 1
+"""
+# bug #5599
+type
+    Base = ref object of RootObj
+    Derived = ref object of Base
+
+method inner(obj: Base) {.base.} =
+    quit "to override"
+
+method outer(obj: Base) {.base.} =
+    echo "outer"
+    obj.inner()
+
+method inner(obj: Derived) =
+    echo "inner Derived"
+
+var x: Derived
+x.outer()