FELIX-2976 fixed the issue by checking if the key is actually in the cache with a null value

git-svn-id: https://svn.apache.org/repos/asf/felix/trunk@1129101 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/dependencymanager/core/src/main/java/org/apache/felix/dm/InvocationUtil.java b/dependencymanager/core/src/main/java/org/apache/felix/dm/InvocationUtil.java
index f59d01c..e6664d2 100644
--- a/dependencymanager/core/src/main/java/org/apache/felix/dm/InvocationUtil.java
+++ b/dependencymanager/core/src/main/java/org/apache/felix/dm/InvocationUtil.java
@@ -92,6 +92,10 @@
             if (m != null) {
                 return m;
             }
+            else if (m_methodCache.containsKey(key)) {
+                // the key is in our cache, it just happens to have a null value
+                return null;
+            }
         }
         // then do a lookup
         try {