Try to recover from corrupt metadata cache

app/src/main/java/com/stevesoltys/seedvault/metadata/MetadataManager.kt

@@ -46,8 +46,12 @@ internal class MetadataManager(
                 field = try {
                     getMetadataFromCache() ?: throw IOException()
                 } catch (e: IOException) {
-                    // If this happens, it is hard to recover from this. Let's hope it never does.
-                    throw AssertionError("Error reading metadata from cache", e)
+                    // This can happen if the storage location ran out of space
+                    // or the app process got killed while writing the file.
+                    // It is hard to recover from this, so we try as best as we can here:
+                    Log.e(TAG, "ERROR getting metadata cache, creating new file ", e)
+                    // This should cause requiresInit() return true
+                    uninitializedMetadata.copy(version = (-1).toByte())
                 }
                 mLastBackupTime.postValue(field.time)
             }

app/src/main/java/com/stevesoltys/seedvault/transport/backup/BackupCoordinator.kt

@@ -231,6 +231,7 @@ internal class BackupCoordinator(
     ): Int {
         state.cancelReason = UNKNOWN_ERROR
         if (metadataManager.requiresInit) {
+            Log.w(TAG, "Metadata requires re-init!")
             // start a new restore set to upgrade from legacy format
             // by starting a clean backup with all files using the new version
             try {