Make containsKey return true if the key is present and the value is n…

…ull in NullableConcurrentHashMap (#320)

* Make containsKey return true if the key is present and the value is null

* Update TestGenericsInvocUnchecked test

src/org/jetbrains/java/decompiler/util/collections/NullableConcurrentHashMap.java

@@ -44,7 +44,7 @@ public boolean containsKey(Object key) {
       key = NULL_KEY;
     }
 
-    return super.containsKey(key);
+    return super.get(key) != null;
   }
 
   @Override

testData/results/pkg/TestGenericsInvocUnchecked.dec

@@ -2,7 +2,7 @@ package pkg;
 
 public class TestGenericsInvocUnchecked<T extends Number> {
    public void test(int i, TestGenericsInvocUnchecked<?> other) {
-      new TestGenericsInvocUnchecked.Inner().testInner(i, this, (TestGenericsInvocUnchecked<T>)other);// 11
+      new TestGenericsInvocUnchecked.Inner().testInner(i, this, other);// 11
    }// 12
 
    public void test1(Class<?> c, String s) {