Add the proper getErrors() method to CellCreator.

Fix the impossibility of the Exterior Cell creation.

apps/opencs/view/world/cellcreator.cpp

@@ -106,3 +106,17 @@ void CSVWorld::CellCreator::cloneMode(const std::string& originId,
         mType->setCurrentIndex(0);
     }
 }
+
+std::string CSVWorld::CellCreator::getErrors() const
+{
+    std::string errors;
+    if (mType->currentIndex() == 0)
+    {
+        errors = GenericCreator::getErrors();
+    }
+    else if (getData().hasId(getId()))
+    {
+        errors = "The Exterior Cell is already exist";
+    }
+    return errors;
+}

apps/opencs/view/world/cellcreator.hpp

@@ -35,6 +35,10 @@ namespace CSVWorld
             virtual void cloneMode(const std::string& originId, 
                                    const CSMWorld::UniversalId::Type type);
 
+            virtual std::string getErrors() const;
+            ///< Return formatted error descriptions for the current state of the creator. if an empty
+            /// string is returned, there is no error.
+
         private slots:
 
             void setType (int index);