Use isHTML*Element() helpers more in the accessibility code

Source/build/scripts/templates/ElementTypeHelpers.h.tmpl

Index: Source/build/scripts/templates/ElementTypeHelpers.h.tmpl
diff --git a/Source/build/scripts/templates/ElementTypeHelpers.h.tmpl b/Source/build/scripts/templates/ElementTypeHelpers.h.tmpl
index 91758aa6e889d33a584bb2efb6a3ad4de8dc5967..b9d45fcde0d476d21bf34fbab2ba8fa8be214ed0 100644
--- a/Source/build/scripts/templates/ElementTypeHelpers.h.tmpl
+++ b/Source/build/scripts/templates/ElementTypeHelpers.h.tmpl
@@ -26,9 +26,9 @@ inline bool is{{tag.interface}}(const Element& element) {
 {%- endif %}
     return element.hasTagName({{namespace}}Names::{{tag.name}}Tag);
 }
-inline bool is{{tag.interface}}(const Element* element) { ASSERT(element); return is{{tag.interface}}(*element); }
+inline bool is{{tag.interface}}(const Element* element) { return element && is{{tag.interface}}(*element); }
 inline bool is{{tag.interface}}(const Node& node) { return node.isElementNode() ? is{{tag.interface}}(toElement(node)) : false; }
-inline bool is{{tag.interface}}(const Node* node) { ASSERT(node); return node->isElementNode() ? is{{tag.interface}}(*toElement(node)) : false; }
+inline bool is{{tag.interface}}(const Node* node) { return node && node->isElementNode() ? is{{tag.interface}}(*toElement(node)) : false; }
 template <> inline bool isElementOfType<const {{tag.interface}}>(const Element& element) { return is{{tag.interface}}(element); }
 {% endfor %}