loader: Prevent crash from VK_KHR_display

Previously, we assumed that the extension VK_KHR_display would be
available on all systems. This appears to no longer be the case. If we
get two ICDs, one which supports the extension and one which does not,
we used to get a crash if trying to call any function from the
extension on the physical device which did not support it. This solves
that crash

loader/wsi.c

@@ -1620,9 +1620,8 @@ VKAPI_ATTR VkResult VKAPI_CALL terminator_GetPhysicalDeviceDisplayPropertiesKHR(
     }
 
     if (NULL == icd_term->dispatch.GetPhysicalDeviceDisplayPropertiesKHR) {
-        loader_log(ptr_instance, VK_DEBUG_REPORT_ERROR_BIT_EXT, 0,
-                   "ICD for selected physical device is not exporting vkGetPhysicalDeviceDisplayPropertiesKHR!\n");
-        assert(false && "loader: null GetPhysicalDeviceDisplayPropertiesKHR ICD pointer");
+        *pPropertyCount = 0;
+        return VK_SUCCESS;
     }
 
     return icd_term->dispatch.GetPhysicalDeviceDisplayPropertiesKHR(phys_dev_term->phys_dev, pPropertyCount, pProperties);
@@ -1651,9 +1650,8 @@ VKAPI_ATTR VkResult VKAPI_CALL terminator_GetPhysicalDeviceDisplayPlanePropertie
     }
 
     if (NULL == icd_term->dispatch.GetPhysicalDeviceDisplayPlanePropertiesKHR) {
-        loader_log(ptr_instance, VK_DEBUG_REPORT_ERROR_BIT_EXT, 0,
-                   "ICD for selected physical device is not exporting vkGetPhysicalDeviceDisplayPlanePropertiesKHR!\n");
-        assert(false && "loader: null GetPhysicalDeviceDisplayPlanePropertiesKHR ICD pointer");
+        *pPropertyCount = 0;
+        return VK_SUCCESS;
     }
 
     return icd_term->dispatch.GetPhysicalDeviceDisplayPlanePropertiesKHR(phys_dev_term->phys_dev, pPropertyCount, pProperties);