fix(flash): Check for I/O failure during firmware file reading

Author: JakubVanek

src/bl_install.c

@@ -66,6 +66,12 @@ int bootloader_install(FILE *fp)
 {
 	u8 *firmware = calloc(FLASH_SIZE, 1);
 	int read_bytes = fread(firmware, 1, FLASH_SIZE, fp); // this may be less than FLASH_SIZE (e.g. Pybricks has a small firmware image)
+	if (ferror(fp)) {
+		errmsg = "Reading of firmware file failed";
+		free(firmware);
+		return ERR_IO;
+	}
+
 	int sector_count = (read_bytes + FLASH_SECTOR_SIZE - 1) / FLASH_SECTOR_SIZE;
 
 	printf("Programming %d EV3 flash sectors...\n", sector_count);