Fix: Handle null or empty release list in `getLatestRelease` (#1967)

app/src/main/java/com/geeksville/mesh/repository/api/FirmwareReleaseLocalDataSource.kt

@@ -52,8 +52,12 @@ class FirmwareReleaseLocalDataSource @Inject constructor(
     suspend fun getLatestRelease(releaseType: FirmwareReleaseType): FirmwareReleaseEntity? =
         withContext(Dispatchers.IO) {
             val releases = firmwareReleaseDao.getReleasesByType(releaseType)
+            if (releases.isNullOrEmpty()) {
+                return@withContext null
+            } else {
                 val latestRelease =
-                releases?.maxBy { it.asDeviceVersion() }
+                    releases.maxBy { it.asDeviceVersion() }
                 return@withContext latestRelease
             }
+        }
 }