Truncate correct position on torn write

Author: albe

src/Partition/ReadablePartition.js

@@ -363,7 +363,7 @@ class ReadablePartition extends events.EventEmitter {
             }
             position -= this.readBufferLength;
         } while (position > 0);
-        return position;
+        return Math.max(0, position);
     }
 
     /**

src/Storage/WritableStorage.js

@@ -86,7 +86,7 @@ class WritableStorage extends ReadableStorage {
             partition.open();
             const tornSequenceNumber = partition.checkTornWrite();
             if (tornSequenceNumber >= 0) {
-                lastValidSequenceNumber = Math.min(lastValidSequenceNumber, tornSequenceNumber - 1);
+                lastValidSequenceNumber = Math.min(lastValidSequenceNumber, tornSequenceNumber);
             }
         });
         if (lastValidSequenceNumber < Number.MAX_SAFE_INTEGER) {