sparse_fuzzer: Bug fix

Resolved Memory Leak

Test: ./sparse_fuzzer clusterfuzz-testcase-minimized-sparse_fuzzer-6050329726943232
Bug: 214604770

Change-Id: I8df4be935ff586efeebf7e32dccc52dbf82e5076
diff --git a/libsparse/sparse_fuzzer.cpp b/libsparse/sparse_fuzzer.cpp
index 235d15d..663c812 100644
--- a/libsparse/sparse_fuzzer.cpp
+++ b/libsparse/sparse_fuzzer.cpp
@@ -23,5 +23,7 @@
   if (!file) {
       return 0;
   }
-  return sparse_file_callback(file, false, false, WriteCallback, nullptr);
+  int32_t result = sparse_file_callback(file, false, false, WriteCallback, nullptr);
+  sparse_file_destroy(file);
+  return result;
 }