Fix SmaliMethodReference.getReturnType() on missing return type
diff --git a/smalidea/src/main/java/org/jf/smalidea/psi/impl/SmaliMethodReference.java b/smalidea/src/main/java/org/jf/smalidea/psi/impl/SmaliMethodReference.java
index 26dcaef..907306a 100644
--- a/smalidea/src/main/java/org/jf/smalidea/psi/impl/SmaliMethodReference.java
+++ b/smalidea/src/main/java/org/jf/smalidea/psi/impl/SmaliMethodReference.java
@@ -124,7 +124,9 @@
     @Nullable
     public SmaliTypeElement getReturnType() {
         SmaliTypeElement[] types = findChildrenByClass(SmaliTypeElement.class);
-        assert types.length == 2;
+        if (types.length < 2) {
+            return null;
+        }
         return types[1];
     }