Fix potential linear alloc memory leak

Previously, if we created a linear alloc for a class loader but
never created the class table, the linear alloc would never get
freed since it would have no corresponding ClassLoaderData.

Fixes valgrind-test-art-host-gtest-oat_test

Bug: 27384882
Change-Id: Ic8f35b58c3117127a39521b6b9d25ef12c72040c
diff --git a/runtime/stack.cc b/runtime/stack.cc
index b1f1ed6..ee5da8e 100644
--- a/runtime/stack.cc
+++ b/runtime/stack.cc
@@ -739,7 +739,7 @@
       // Check class linker linear allocs.
       mirror::Class* klass = method->GetDeclaringClass();
       LinearAlloc* const class_linear_alloc = (klass != nullptr)
-          ? ClassLinker::GetAllocatorForClassLoader(klass->GetClassLoader())
+          ? runtime->GetClassLinker()->GetAllocatorForClassLoader(klass->GetClassLoader())
           : linear_alloc;
       if (!class_linear_alloc->Contains(method)) {
         // Check image space.