ART: Allow uninitialized runtime in oat code

Oatdump does not initialize a runtime. Avoid a segfault.

Bug: 17194559
Change-Id: I1a1bd3fc7762ff4714251617a975e832522fa879
diff --git a/runtime/oat_file.cc b/runtime/oat_file.cc
index 9afad2b..6305994 100644
--- a/runtime/oat_file.cc
+++ b/runtime/oat_file.cc
@@ -531,7 +531,9 @@
     methods_pointer_index = num_set_bits;
   }
   const OatMethodOffsets& oat_method_offsets = methods_pointer_[methods_pointer_index];
-  if (oat_file_->IsExecutable() || Runtime::Current()->IsCompiler()) {
+  if (oat_file_->IsExecutable() ||
+      Runtime::Current() == nullptr ||        // This case applies for oatdump.
+      Runtime::Current()->IsCompiler()) {
     return OatMethod(
         oat_file_->Begin(),
         oat_method_offsets.code_offset_,