Add check in splitCells to prevent calling trim on undefined (#2372)

Author: zbialecki

src/helpers.js

@@ -162,7 +162,7 @@ export function splitCells(tableRow, count) {
 
   // First/last cell in a row cannot be empty if it has no leading/trailing pipe
   if (!cells[0].trim()) { cells.shift(); }
-  if (!cells[cells.length - 1].trim()) { cells.pop(); }
+  if (cells.length > 0 && !cells[cells.length - 1].trim()) { cells.pop(); }
 
   if (cells.length > count) {
     cells.splice(count);

test/specs/new/nbsp_following_tables.html

@@ -0,0 +1,22 @@
+<table>
+  <thead>
+    <tr>
+      <th>abc</th>
+      <th>def</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <td>bar</td>
+      <td>foo</td>
+    </tr>
+    <tr>
+      <td>baz</td>
+      <td>boo</td>
+    </tr>
+    <tr>
+      <td></td>
+      <td></td>
+    </tr>
+  </tbody>
+</table>

test/specs/new/nbsp_following_tables.md

@@ -0,0 +1,5 @@
+| abc | def |
+| --- | --- |
+| bar | foo |
+| baz | boo |
+