Fix Qt 0.14.2->0.15.0 segfault if "total at least" is selected

A button was removed, so now button(1) is nullptr

src/qt/sendcoinsdialog.cpp

@@ -128,7 +128,7 @@ SendCoinsDialog::SendCoinsDialog(const PlatformStyle *_platformStyle, QWidget *p
     ui->groupFee->setId(ui->radioCustomFee, 1);
     ui->groupFee->button((int)std::max(0, std::min(1, settings.value("nFeeRadio").toInt())))->setChecked(true);
     ui->groupCustomFee->setId(ui->radioCustomPerKilobyte, 0);
-    ui->groupCustomFee->button((int)std::max(0, std::min(1, settings.value("nCustomFeeRadio").toInt())))->setChecked(true);
+    ui->groupCustomFee->button(0)->setChecked(true);
     ui->customFee->setValue(settings.value("nTransactionFee").toLongLong());
     ui->checkBoxMinimumFee->setChecked(settings.value("fPayOnlyMinFee").toBool());
     minimizeFeeSection(settings.value("fFeeSectionMinimized").toBool());