This commit fixes trac:1002.

Protect the free and strdup values for replacing keyval pairs just as we do 
below in the files for new keyval pairs.

In basic testing this seems to make everything work as it should again.

This commit was SVN r14460.

The following Trac tickets were found above:
  Ticket 1002 --> https://svn.open-mpi.org/trac/ompi/ticket/1002

opal/mca/base/mca_base_parse_paramfile.c

@@ -50,8 +50,14 @@ static void save_value(const char *name, const char *value)
          item = opal_list_get_next(item)) {
         fv = (mca_base_param_file_value_t *) item;
         if (0 == strcmp(name, fv->mbpfv_param)) {
-            free(fv->mbpfv_value);
+            if (NULL != fv->mbpfv_value ) {
-            fv->mbpfv_value = strdup(value);
+                free(fv->mbpfv_value);
+            }
+            if (NULL != value) {
+                fv->mbpfv_value = strdup(value);
+            } else {
+                fv->mbpfv_value = NULL;
+            }
             return;
         }
     }