Merge bitcoin#11508: Fix crash via division by zero assertion

207408b Fix crash via division by zero assertion (Jonas Schnelli)

Pull request description:

  Replaces the newly added `assert` for a devision by zero protection by a control structure. Floating point division by zero is defined by the floating point standard and results in +inf or -inf.

  Introduced in bitcoin#11133
  Reported by @mzhou, fixes bitcoin#11501

Tree-SHA512: ac9b4efa3ba52a2aa246fb11170128c4aaf829fd491b649524c85069c6ed33ae612e761809aea9d9a44bdea29a417b3f3a558226495094b5070a42a56b2ac77e

src/qt/coincontroldialog.cpp

@@ -628,8 +628,7 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
     QString toolTipDust = tr("This label turns red if any recipient receives an amount smaller than the current dust threshold.");
 
     // how many satoshis the estimated fee can vary per byte we guess wrong
-    assert(nBytes != 0);
-    double dFeeVary = (double)nPayFee / nBytes;
+    double dFeeVary = (nBytes != 0) ? (double)nPayFee / nBytes : 0;
 
     QString toolTip4 = tr("Can vary +/- %1 duff(s) per input.").arg(dFeeVary);