test: Fix HIL write-bin test

Author: SergioGasquez

espflash/src/bin/espflash.rs

@@ -350,7 +350,10 @@ fn write_bin(args: WriteBinArgs, config: &Config) -> Result<()> {
 
     // If the file size is not divisible by 4, we need to pad `FF` bytes to the end
     let size = f.metadata().into_diagnostic()?.len();
-    let padded_bytes = 4 - (size % 4);
+    let mut padded_bytes = 0;
+    if size % 4 != 0 {
+        padded_bytes = 4 - (size % 4);
+    }
     let mut buffer = Vec::with_capacity(size.try_into().into_diagnostic()?);
     f.read_to_end(&mut buffer).into_diagnostic()?;
     buffer.extend_from_slice(&vec![0xFF; padded_bytes as usize]);