Fix a small bug in parameter processing that would always result

in at least on entry in a VectorParam even if the string was
empty.

sim/param.cc:
    if there are no parameters, leave the vector empty.

--HG--
extra : convert_revision : d0d41baa8c77651a27ac6a4d02cc388711f47dbe

sim/param.cc

@@ -211,6 +211,11 @@ template <class T>
 void
 VectorParam<T>::parse(const string &s)
 {
+    if (s.empty()) {
+        wasSet = true;
+        return;
+    }
+
     vector<string> tokens;
 
     tokenize(tokens, s, ' ');