Skip attachments without any content for events (#5110)

<!-- PR description-->

Known issue, tracking in https://github.com/alcionai/corso/issues/4772

---

#### Does this PR need a docs update or release note?

- [ ] ✅ Yes, it's included
- [ ] 🕐 Yes, but in a later PR
- [x] ⛔ No

#### Type of change

<!--- Please check the type of change your PR introduces: --->
- [ ] 🌻 Feature
- [x] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Supportability/Tests
- [ ] 💻 CI/Deployment
- [ ] 🧹 Tech Debt/Cleanup

#### Issue(s)

<!-- Can reference multiple issues. Use one of the following "magic words" - "closes, fixes" to auto-close the Github issue. -->
* #<issue>

#### Test Plan

<!-- How will this be tested prior to merging.-->
- [ ] 💪 Manual
- [ ] ⚡ Unit test
- [ ] 💚 E2E

src/internal/converters/eml/eml.go

@@ -237,15 +237,12 @@ func FromJSON(ctx context.Context, body []byte) (string, error) {
 			}
 
 			if bytes == nil {
-				// Some attachments have an "item" field instead of
+				// TODO(meain): Handle non file attachments
-				// "contentBytes". There are items like contacts, emails
-				// or calendar events which will not be a normal format
-				// and will have to be converted to a text format.
-				// TODO(meain): Handle custom attachments
 				// https://github.com/alcionai/corso/issues/4772
 				logger.Ctx(ctx).
-					With("attachment_id", ptr.Val(attachment.GetId())).
+					With("attachment_id", ptr.Val(attachment.GetId()),
-					Info("unhandled attachment type")
+						"attachment_type", ptr.Val(attachment.GetOdataType())).
+					Info("no contentBytes for attachment")
 
 				continue
 			}

src/internal/converters/ics/ics.go

@@ -17,6 +17,7 @@ import (
 	"github.com/alcionai/corso/src/internal/common/ptr"
 	"github.com/alcionai/corso/src/internal/common/str"
 	"github.com/alcionai/corso/src/pkg/dttm"
+	"github.com/alcionai/corso/src/pkg/logger"
 	"github.com/alcionai/corso/src/pkg/services/m365/api"
 )
 
@@ -527,7 +528,6 @@ func updateEventProperties(ctx context.Context, event models.Eventable, iCalEven
 	}
 
 	// ATTACH - https://www.rfc-editor.org/rfc/rfc5545#section-3.8.1.1
-	// TODO Handle different attachment types (file, item and reference)
 	attachments := event.GetAttachments()
 	for _, attachment := range attachments {
 		props := []ics.PropertyParameter{}
@@ -548,6 +548,17 @@ func updateEventProperties(ctx context.Context, event models.Eventable, iCalEven
 			return clues.WrapWC(ctx, err, "getting attachment content")
 		}
 
+		if cb == nil {
+			// TODO(meain): Handle non file attachments
+			// https://github.com/alcionai/corso/issues/4772
+			logger.Ctx(ctx).
+				With("attachment_id", ptr.Val(attachment.GetId()),
+					"attachment_type", ptr.Val(attachment.GetOdataType())).
+				Info("no contentBytes for attachment")
+
+			continue
+		}
+
 		content, ok := cb.([]uint8)
 		if !ok {
 			return clues.NewWC(ctx, "getting attachment content string").