Segfault less during consensus generation without params

If no authority votes on any params, Tor authorities segfault when
trying to make a new consensus from the votes. Let's change that.

changes/dont_segfault_while_making_consensus_without_params

+  o Minor bugfixes:
+    - When none of the authorities vote on any params, Tor segfaults when
+      trying to make the consensus from the votes. This is currently
+      not critical, because authorities do include params in their votes.
+      Bugfix on 0.2.2.10-alpha, fixes bug 1322.

src/or/dirvote.c

@@ -1757,10 +1757,12 @@ networkstatus_compute_consensus(smartlist_t *votes,
     // Parse params, extract BW_WEIGHT_SCALE if present
     // DO NOT use consensus_param_bw_weight_scale() in this code!
     // The consensus is not formed yet!
-    if (strcmpstart(params, "bwweightscale=") == 0)
-      bw_weight_param = params;
-    else
-      bw_weight_param = strstr(params, " bwweightscale=");
+    if (params) {
+      if (strcmpstart(params, "bwweightscale=") == 0)
+        bw_weight_param = params;
+      else
+        bw_weight_param = strstr(params, " bwweightscale=");
+    }
 
     if (bw_weight_param) {
       int ok=0;