gate the close() on the underlying input stream

Author: supervacuus

sentry-android-core/src/main/java/io/sentry/android/core/internal/tombstone/TombstoneParser.java

@@ -349,6 +349,8 @@ private DebugMeta createDebugMeta(@NonNull final Tombstone tombstone) {
 
   @Override
   public void close() throws IOException {
-    tombstoneStream.close();
+    if (tombstoneStream != null) {
+      tombstoneStream.close();
+    }
   }
 }