Fixed issues found by static analysis

- rolling_median: tried to free uninitialized pointer in a constructor
- net_node.inl: erase-remove idiom was used incorrectly. remove_if doesn't actually remove elements, see http://cpp.sh/6fcjv
- bulletproofs.cc: call to sizeof() instead of vector.size(), luckily it only impacts performance and not code logic there

contrib/epee/include/rolling_median.h

@@ -141,7 +141,6 @@ public:
 
   rolling_median_t(rolling_median_t &&m)
   {
-    free(data);
     memcpy(this, &m, sizeof(rolling_median_t));
     m.data = NULL;
   }