- replace one SGPropertyNode* by SGPropertyNode_ptr to avoid crash with

temporary removeChild(); should be done even after reverting; the node
  is accessed after removal
- cleanup:  if (foo) delete foo  -->  delete foo

src/AIModel/AIBase.cxx

@@ -76,7 +76,7 @@ FGAIBase::~FGAIBase() {
     // unbind();
     SGPropertyNode *root = globals->get_props()->getNode("ai/models", true);
     root->removeChild(_type_str.c_str(), index);
-    if (fp) delete fp;
+    delete fp;
     fp = NULL;
 }
 

src/AIModel/AIBase.hxx

@@ -119,7 +119,7 @@ public:
 
 protected:
 
-    SGPropertyNode *props;
+    SGPropertyNode_ptr props;
     FGAIManager* manager;
 
     // these describe the model's actual state