Fix a few "Uninitialized scalar field" warnings

Fix a few warnings reported by Coverity.
None of these is critical, but making sure that class fields are
initialized can avoid heisenbugs.

src/bloom.h

@@ -60,7 +60,7 @@ public:
     // It should generally always be a random value (and is largely only exposed for unit testing)
     // nFlags should be one of the BLOOM_UPDATE_* enums (not _MASK)
     CBloomFilter(unsigned int nElements, double nFPRate, unsigned int nTweak, unsigned char nFlagsIn);
-    CBloomFilter() : isFull(true) {}
+    CBloomFilter() : isFull(true), isEmpty(false), nHashFuncs(0), nTweak(0), nFlags(0) {}
 
     IMPLEMENT_SERIALIZE
     (