Fix bootSha1 Hash not found case.

Fix crash when bootsha1 not found in json file.

Author: fatalcoder524

app/src/main/java/com/github/capntrips/kernelflasher/ui/screens/backups/BackupsContent.kt

@@ -46,7 +46,7 @@ fun ColumnScope.BackupsContent(
             if (currentBackup.type == "raw") {
                 DataRow(
                     label = stringResource(R.string.boot_sha1),
-                    value = currentBackup.bootSha1!!.substring(0, 8),
+                    value = currentBackup.bootSha1?.substring(0, 8) ?: "",
                     valueStyle = MaterialTheme.typography.titleSmall.copy(
                         fontFamily = FontFamily.Monospace,
                         fontWeight = FontWeight.Medium
@@ -122,7 +122,7 @@ fun ColumnScope.BackupsContent(
                     if (currentBackup.type == "raw") {
                         DataRow(
                             label = stringResource(R.string.boot_sha1),
-                            value = currentBackup.bootSha1!!.substring(0, 8),
+                            value = currentBackup.bootSha1?.substring(0, 8) ?: "",
                             valueStyle = MaterialTheme.typography.titleSmall.copy(
                                 fontFamily = FontFamily.Monospace,
                                 fontWeight = FontWeight.Medium