test better detail combined view

app/UI/VmUpdate/Sections/Qemu/AdditionalDiskSection.php

@@ -31,7 +31,7 @@ class AdditionalDiskSection extends BaseSection implements ClientArea
         $rangeField = $this->getField('additionalDiskSize');
         $rangeField->setMinValue($diskSize);
         $rangeField->setDefaultValue($diskSize);
-        if ($this->configuration()->serverDiskSize->max > ($this->resourceManager->disk()->free() + $diskSize)) {
+        if ($this->configuration()->serverDiskSize->max > ($this->resourceManager->disk()->free())) {
             $rangeField->setMaxValue($this->resourceManager->disk()->free() + $diskSize);
         } else {
             $rangeField->setMaxValue($this->configuration()->serverDiskSize->max);