Don't call AddImageStringsToTable or MoveImageClassesToClassTable if running imageless

If we fail to create the image we use imageless running, this was
breaking AddImageStringsToTable since we didn't check for this
case. Added a check which avoids calling AddImageStringsToTable and
MoveImageClassesToClassTable if we don't have an image.

Bug: 18412472

(cherry picked from commit ab1953f35880f94752e1fcde3f6b3f0d3532125b)

Change-Id: Ida18e1fcd04d752d55923e65c3122c0ac0bde728
diff --git a/runtime/runtime.cc b/runtime/runtime.cc
index 78c6542..d50a4f0 100644
--- a/runtime/runtime.cc
+++ b/runtime/runtime.cc
@@ -440,8 +440,11 @@
 
   if (IsZygote()) {
     ScopedObjectAccess soa(self);
-    Runtime::Current()->GetInternTable()->AddImageStringsToTable(heap_->GetImageSpace());
-    Runtime::Current()->GetClassLinker()->MoveImageClassesToClassTable();
+    gc::space::ImageSpace* image_space = heap_->GetImageSpace();
+    if (image_space != nullptr) {
+      Runtime::Current()->GetInternTable()->AddImageStringsToTable(image_space);
+      Runtime::Current()->GetClassLinker()->MoveImageClassesToClassTable();
+    }
   }
 
   if (!IsImageDex2OatEnabled() || !Runtime::Current()->GetHeap()->HasImageSpace()) {