XWIKI-19154: Cannot display icons on reset password template

  * Avoid a NPE when the context doc is null
  * Document that XWikiContext#getDoc can be null

(cherry picked from commit 3cdb378e)

xwiki-platform-core/xwiki-platform-oldcore/src/main/java/com/xpn/xwiki/XWikiContext.java

@@ -512,6 +512,9 @@ public boolean isMainWiki(String wikiName)
         return StringUtils.equalsIgnoreCase(wikiName, getMainXWiki());
     }
 
+    /**
+     * @return the current document handled in the context or {@code null}.
+     */
     public XWikiDocument getDoc()
     {
         return (XWikiDocument) get("doc");

xwiki-platform-core/xwiki-platform-skin/xwiki-platform-skin-skinx/src/main/java/com/xpn/xwiki/plugin/skinx/AbstractDocumentSkinExtensionPlugin.java

@@ -236,14 +236,16 @@ public Set<DocumentReference> getAlwaysUsedExtensions()
     public boolean hasPageExtensions(XWikiContext context)
     {
         XWikiDocument doc = context.getDoc();
-        List<BaseObject> objects = doc.getObjects(getExtensionClassName());
-        if (objects != null) {
-            for (BaseObject obj : objects) {
-                if (obj == null) {
-                    continue;
-                }
-                if (obj.getStringValue(USE_FIELDNAME).equals("currentPage")) {
-                    return true;
+        if (doc != null) {
+            List<BaseObject> objects = doc.getObjects(getExtensionClassName());
+            if (objects != null) {
+                for (BaseObject obj : objects) {
+                    if (obj == null) {
+                        continue;
+                    }
+                    if (obj.getStringValue(USE_FIELDNAME).equals("currentPage")) {
+                        return true;
+                    }
                 }
             }
         }