video_capture: chromeos: check for metadata with invalid data

In case a metadata is returned with valid tag but no data, count the
metadata entry as invalid.

Bug: 1155255
Test: compile and manually verify that camera works on DUT
Change-Id: I663ba5cdab177d95c83a77546c70ffd9122157f3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2620741
Commit-Queue: Ricky Liang <jcliang@chromium.org>
Reviewed-by: Wei Lee <wtlee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841938}

media/capture/video/chromeos/camera_metadata_utils.cc

@@ -56,7 +56,15 @@ cros::mojom::CameraMetadataEntryPtr* GetMetadataEntry(
   if (iter == camera_metadata->entries.value().end()) {
     return nullptr;
   }
-  return &(camera_metadata->entries.value()[(*iter)->index]);
+
+  auto* entry_ptr = &(camera_metadata->entries.value()[(*iter)->index]);
+  if (!(*entry_ptr)->data.data()) {
+    // Metadata tag found with no valid data.
+    LOG(WARNING) << "Found tag " << static_cast<int>(tag)
+                 << " but with invalid data";
+    return nullptr;
+  }
+  return entry_ptr;
 }
 
 void AddOrUpdateMetadataEntry(cros::mojom::CameraMetadataPtr* to,