inliner: Do not assume that the outermost_graph has an art method

The outermost method may be in an unresolved class. If that's the case
do not assume anything about the referrer in HLoadClass.

Test: m test-art-host
Bug: 37588888
Change-Id: I1a59325740ac9c5bcadc12661f5a82f642747bf9
diff --git a/test/648-inline-caches-unresolved/info.txt b/test/648-inline-caches-unresolved/info.txt
new file mode 100644
index 0000000..8fc6042
--- /dev/null
+++ b/test/648-inline-caches-unresolved/info.txt
@@ -0,0 +1 @@
+Test for inlining with inline cache into an unresolved method.