bug #847: Fix constness for erase method in PoolObjectSQL. Better check in template erase

include/PoolObjectSQL.h

@@ -216,7 +216,7 @@ public:
      */
     int erase_template_attribute(
         const char * name,
-        string&      value) const
+        string&      value)
     {
         obj_template->get(name,value);
         return obj_template->erase(name);

src/template/Template.cc

@@ -215,6 +215,11 @@ int Template::erase(const string& name)
 
     index = attributes.equal_range(name);
 
+    if (index.first == index.second )
+    {
+        return 0;
+    }
+
     for ( i = index.first,j=0 ; i != index.second ; i++,j++ )
     {
         Attribute * attr = i->second;