Fix a corner case with combine_header_slug and Tab and Tabbed

If there is no header before the tab, code could break

Author: facelessuser

docs/src/markdown/about/changelog.md

@@ -1,5 +1,10 @@
 # Changelog
 
+## Unreleased
+
+-   **FIX**: Tab and Tabbed: Fix a case where tabs could fail if `combine_header_slug` was enabled and there was no
+    header.
+
 ## 10.14.3
 
 -   **FIX**: Blocks: An empty, raw block type should not cause an error.

pymdownx/blocks/tab.py

@@ -36,7 +36,7 @@ def get_parent_header_slug(self, root, header_map, parent_map, el):
                 for i in list(parent):
                     if i is el and header is None:
                         break
-                    if i is last_parent:
+                    if i is last_parent and header is not None:
                         return header.attrib.get("id", '')
                     if i in headers:
                         header = i

pymdownx/tabbed.py

@@ -327,7 +327,7 @@ def get_parent_header_slug(self, root, header_map, parent_map, el):
                 for i in list(parent):
                     if i is el and header is None:
                         break
-                    if i is last_parent:
+                    if i is last_parent and header is not None:
                         return header.attrib.get("id", '')
                     if i in headers:
                         header = i