fix insert image

lib/models/documents/document.dart

@@ -173,12 +173,18 @@ class Document {
     for (int i = 0; i < ops.length; i++) {
       Operation op = ops[i];
       res.push(op);
+      bool nextOpIsImage = i + 1 < ops.length &&
+          ops[i + 1].isInsert &&
+          ops[i + 1].data is !String;
+      if (nextOpIsImage && !(op.data as String).endsWith('\n')){
+        res.push(Operation.insert('\n', null));
+      }
       // Currently embed is equivalent to image and hence `is! String`
       bool opInsertImage = op.isInsert && op.data is! String;
       bool nextOpIsLineBreak = i + 1 < ops.length &&
           ops[i + 1].isInsert &&
           ops[i + 1].data is String &&
-          (ops[i + 1].data as String) == '\n';
+          (ops[i + 1].data as String).startsWith('\n');
       if (opInsertImage && (i + 1 == ops.length - 1 || !nextOpIsLineBreak)) {
         // automatically append '\n' for image
         res.push(Operation.insert('\n', null));