Added default metadata entries.

Default entries for controls/properties that could theoretically
be queried from/controlled by V4L2, but are not yet implemented
in this HAL.

BUG: 30140438
TEST: unit tests pass
Change-Id: I78264f3f0d37b41614b24ef71000fee175a3bb17
diff --git a/modules/camera/3_4/metadata/control.h b/modules/camera/3_4/metadata/control.h
index c0426c1..6442f90 100644
--- a/modules/camera/3_4/metadata/control.h
+++ b/modules/camera/3_4/metadata/control.h
@@ -120,10 +120,18 @@
 
   // Populate with a default.
   T value;
-  int res = options_->DefaultValueForTemplate(template_type, &value);
+  int res;
+  if (options_) {
+    res = options_->DefaultValueForTemplate(template_type, &value);
+  } else {
+    // If there's no options (and thus no default option),
+    // fall back to whatever the current value is.
+    res = delegate_->GetValue(&value);
+  }
   if (res) {
     return res;
   }
+
   return UpdateMetadata(metadata, delegate_->tag(), value);
 }