Fix a memory management issue

Again, we had a Crash during the seeding rounds that resolved to this bug. In kovan_module_p.cpp there was an unchecked use of malloc, which was then immediately dereferenced by the -> operator. As we can see in the [documentation for the standard library](http://www.cplusplus.com/reference/cstdlib/malloc/), malloc can return 0 if the allocation fails, which in turn results in a crash (which is the exact thing that happened to us during seedings). I couldn't test if this "fix" works, but it should at least demonstrate that using malloc without a check if it failed *must* never happen at all.