Re #6190. Beefed up error message for deprecated algorithms.

Sorry, but throwing an exception when the developer didn't specify an
alternate algorithm doesn't always make sense. Sometimes an algorithm
just get dropped from the list of things mantid does.

Code/Mantid/Framework/API/src/DeprecatedAlgorithm.cpp

@@ -52,8 +52,14 @@ namespace API
     if (!this->m_deprecatdDate.empty())
       msg << " (on " << this->m_deprecatdDate << ")";
 
-    if (!this->m_replacementAlgorithm.empty())
-      msg << ". Use " << this->m_replacementAlgorithm << " instead." << std::endl;
+    if (this->m_replacementAlgorithm.empty())
+    {
+      msg << " and has no replacement.";
+    }
+    else
+    {
+      msg << ". Use " << this->m_replacementAlgorithm << " instead.";
+    }
 
     return msg.str();
   }