do not show potential invoices with a negative total (#3579)

src/Invoice/Calculator/AbstractCalculator.php

@@ -48,7 +48,7 @@ abstract class AbstractCalculator
      */
     public function getSubtotal(): float
     {
-        $amount = 0;
+        $amount = 0.00;
         foreach ($this->model->getEntries() as $entry) {
             $amount += $entry->getRate();
         }

src/Invoice/ServiceInvoice.php

@@ -590,6 +590,10 @@ final class ServiceInvoice
             $model->addEntries($settings['entries']);
             $this->prepareModelQueryDates($model);
 
+            if ($model->getCalculator()->getTotal() < 0.0) {
+                continue;
+            }
+
             $models[] = $model;
         }