content: Handle blank text nodes after code blocks

Fixes: #355

Author: Khader-1

lib/model/content.dart

@@ -1107,7 +1107,7 @@ class _ZulipContentParser {
     for (final node in nodes) {
       // We get a bunch of newline Text nodes between paragraphs.
       // A browser seems to ignore these; let's do the same.
-      if (node is dom.Text && (node.text == '\n')) continue;
+      if (node is dom.Text && RegExp(r'^\n+$').hasMatch(node.text)) continue;
 
       final block = parseBlockContent(node);
       if (block is ImageNode) {

test/model/content_test.dart

@@ -301,6 +301,21 @@ class ContentExample {
         '\n</code></pre></div>'),
     ]);
 
+  static const lineBreaksAfterCodeBlocks = ContentExample(
+    'blank text nodes after code blocks',
+    '    code block.\n\nsome content',
+    '<div class="codehilite">'
+      '<pre><span></span><code>'
+        'code block.\n'
+      '</code></pre>'
+    '</div>\n\n'
+    '<p>'
+      'some content'
+    '</p>', [
+      CodeBlockNode([CodeBlockSpanNode(text: "code block.", type: CodeBlockSpanType.text)]),
+      ParagraphNode(links: null, nodes: [TextNode("some content")]),
+    ]);
+
   static final mathInline = ContentExample.inline(
     'inline math',
     r"$$ \lambda $$",
@@ -843,6 +858,7 @@ void main() {
   testParseExample(ContentExample.codeBlockHighlightedMultiline);
   testParseExample(ContentExample.codeBlockWithHighlightedLines);
   testParseExample(ContentExample.codeBlockWithUnknownSpanType);
+  testParseExample(ContentExample.lineBreaksAfterCodeBlocks);
 
   testParseExample(ContentExample.mathBlock);
   testParseExample(ContentExample.mathBlockInQuote);