Fix GetInnerText skipping table tabs/newlines when HTML has whitespace between elements

Use NextElementSibling instead of NextSibling for table cell and row
sibling checks, so whitespace text nodes between elements don't prevent
tab/newline insertion.

Author: jafin

src/AngleSharp.Css.Tests/Extensions/InnerText.cs

@@ -47,6 +47,7 @@ public void SetInnerText(String fixture, String expectedInnerText, String expect
         [TestCase("test1<br>test2<br>test3", "test1\ntest2\ntest3")]
         // table
         [TestCase("<table><tr><td>1</td><td>2</td></tr><tr><td>3</td><td>4</td></tr></table>", "1\t2\n3\t4")]
+        [TestCase("<table><tr><td>1</td> <td>2</td></tr> <tr><td>3</td> <td>4</td></tr></table>", "1\t2\n3\t4")]
         [TestCase("<table><tr><td>1</td><td>2</td></tr><tr><td><table><tr><td>3</td><td>4</td></tr></table></td><td>5</td></tr></table>", "1\t2\n\n3\t4\n\t5")]
         // select
         [TestCase("<select><option>test1</option><option>test2</option></select>", "test1\ntest2")]

src/AngleSharp.Css/Extensions/ElementExtensions.cs

@@ -204,7 +204,7 @@ private static void ItcInCssBox(ICssStyleDeclaration elementStyle, ICssStyleDecl
                 }
                 else if (elementStyle is not null && ((node is IHtmlTableCellElement && String.IsNullOrEmpty(elementStyle.GetDisplay())) || elementStyle.GetDisplay() == CssKeywords.TableCell))
                 {
-                    if (node.NextSibling is IElement nextSibling)
+                    if (((IElement)node).NextElementSibling is IElement nextSibling)
                     {
                         var nextSiblingCss = nextSibling.ComputeCurrentStyle();
 
@@ -216,7 +216,7 @@ private static void ItcInCssBox(ICssStyleDeclaration elementStyle, ICssStyleDecl
                 }
                 else if (elementStyle is not null && ((node is IHtmlTableRowElement && String.IsNullOrEmpty(elementStyle.GetDisplay())) || elementStyle.GetDisplay() == CssKeywords.TableRow))
                 {
-                    if (node.NextSibling is IElement nextSibling)
+                    if (((IElement)node).NextElementSibling is IElement nextSibling)
                     {
                         var nextSiblingCss = nextSibling.ComputeCurrentStyle();