fix: return error when trying to import empty objects

echo '{}' | algolia objects import -F- --auto-generate...
used to create an empty record with just the objectID.
I think it's more reasonable to expect it to return an error instead,
as it's likely a user error.

pkg/cmd/objects/import/import.go

@@ -103,10 +103,12 @@ func runImportCmd(opts *ImportOptions) error {
 			err := fmt.Errorf("failed to parse JSON object on line %d: %s", count, err)
 			return err
 		}
-		// The API client doesn't support this flag since v4
-		// The API always automatically generates objectIDs
-		// if you pass in records without them
-		// Implement it here to avoid breaking changes
+
+		if len(record) == 0 {
+			return fmt.Errorf("empty object on line %d", count)
+		}
+		// The API always automatically generates objectIDs for this operation
+		// The v3 API clients implemented this option, but not v4, so we'll implement it here
 		if !opts.AutoObjectIDs {
 			if _, ok := record["objectID"]; !ok {
 				return fmt.Errorf("missing objectID on line %d", count)

pkg/cmd/objects/import/import_test.go

@@ -37,6 +37,12 @@ func Test_runImportCmd(t *testing.T) {
 			cli:     fmt.Sprintf("foo -F '%s'", tmpFile),
 			wantOut: "✓ Successfully imported 1 objects to foo in",
 		},
+		{
+			name:    "empty object",
+			cli:     "foo -F -",
+			stdin:   `{}`,
+			wantErr: "empty object on line 0",
+		},
 		{
 			name:    "missing objectID",
 			cli:     "foo -F -",