Merge #16286: refactoring: wallet: Fix GCC 7.4.0 warning

d8bd97d Fix GCC 7.4.0 warning (Hennadii Stepanov)

Pull request description:

  Having #13756 and #16239 merged cause GCC warning:
  ```
  $ gcc --version
  gcc (Ubuntu 7.4.0-1ubuntu1~18.04.1) 7.4.0
  ...
  $ make -j 4 > /dev/null
  wallet/wallet.cpp: In member function ‘CWallet::Balance CWallet::GetBalance(int, bool) const’:
  wallet/wallet.cpp:2269:45: warning: enumeral and non-enumeral type in conditional expression [-Wextra]
       isminefilter reuse_filter = avoid_reuse ? 0 : ISMINE_USED;
                                   ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~
  ```

  Fixed with this PR.

ACKs for top commit:
  practicalswift:
    utACK d8bd97d
  promag:
    ACK d8bd97d.
  kallewoof:
    utACK d8bd97d
  meshcollider:
    Trivial utACK bitcoin/bitcoin@d8bd97d

Tree-SHA512: 2fb315ac82f290c8b9f4e48d1b4526b9babe0717c68593c7bc55cd6c289e64b6322aba72984f39291a9254b57d3f6ba8dbfe03799f510c0c1dc108b21b286732

Author: fanquake

src/wallet/wallet.cpp

@@ -2266,7 +2266,7 @@ void MaybeResendWalletTxs()
 CWallet::Balance CWallet::GetBalance(const int min_depth, bool avoid_reuse) const
 {
     Balance ret;
-    isminefilter reuse_filter = avoid_reuse ? 0 : ISMINE_USED;
+    isminefilter reuse_filter = avoid_reuse ? ISMINE_NO : ISMINE_USED;
     {
         auto locked_chain = chain().lock();
         LOCK(cs_wallet);