wallet: fix scanning progress calculation for single block range

If the blockchain is rescanned for a single block (i.e. start and stop hashes
are equal, and with that also the estimated verification progress) the progress
calculation could lead to a NaN value caused by a division by zero, resulting in
an invalid JSON result for the getwalletinfo RPC.  Fixed by setting the progress
to zero in that special case.

Co-authored-by: MarcoFalke <falke.marco@gmail.com>

src/wallet/wallet.cpp

@@ -1778,7 +1778,11 @@ CWallet::ScanResult CWallet::ScanForWalletTransactions(const uint256& start_bloc
     double progress_current = progress_begin;
     int block_height = start_height;
     while (!fAbortRescan && !chain().shutdownRequested()) {
-        m_scanning_progress = (progress_current - progress_begin) / (progress_end - progress_begin);
+        if (progress_end - progress_begin > 0.0) {
+            m_scanning_progress = (progress_current - progress_begin) / (progress_end - progress_begin);
+        } else { // avoid divide-by-zero for single block scan range (i.e. start and stop hashes are equal)
+            m_scanning_progress = 0;
+        }
         if (block_height % 100 == 0 && progress_end - progress_begin > 0.0) {
             ShowProgress(strprintf("%s " + _("Rescanning...").translated, GetDisplayName()), std::max(1, std::min(99, (int)(m_scanning_progress * 100))));
         }

test/sanitizer_suppressions/ubsan

@@ -1,7 +1,6 @@
 # -fsanitize=undefined suppressions
 # =================================
 float-divide-by-zero:validation.cpp
-float-divide-by-zero:wallet/wallet.cpp
 
 # -fsanitize=integer suppressions
 # ===============================