Replaced ASSERT() with explicit error handling

During fuzz testing, we encountered an ASSERT() condition
being triggered.

Changes:
- Replaced ASSERT() with explicit condition check
- Returns EFI_DEVICE_ERROR on failure case

Signed-off-by: Pavel Naberezhnev <[email protected]>

Author: Pavel Naberezhnev

Ext4Pkg/Ext4Dxe/File.c

@@ -498,7 +498,9 @@ Ext4ReadFile (
   File      = EXT4_FILE_FROM_THIS (This);
   Partition = File->Partition;
 
-  ASSERT (Ext4FileIsOpenable (File));
+  if (!Ext4FileIsOpenable (File)) {
+    return EFI_DEVICE_ERROR;
+  }
 
   if (Ext4FileIsReg (File)) {
     Status = Ext4Read (Partition, File, Buffer, File->Position, BufferSize);