Fix tiny memory leak

Bug: 36103283
Change-Id: Ib33905fc64b997da80b4b26346db7c531ff8bb8e
diff --git a/media/libstagefright/MPEG4Extractor.cpp b/media/libstagefright/MPEG4Extractor.cpp
index 02be033..71519d2 100644
--- a/media/libstagefright/MPEG4Extractor.cpp
+++ b/media/libstagefright/MPEG4Extractor.cpp
@@ -3005,6 +3005,8 @@
 
         // smallest possible valid UTF-16 string w BOM: 0xfe 0xff 0x00 0x00
         if (size < 6) {
+            delete[] buffer;
+            buffer = NULL;
             return ERROR_MALFORMED;
         }