httplive: check for malformed EXT-X-STREAM-INF

Bug: 68342866
Test: adb shell am start -a android.intent.action.VIEW -d http://localhost:1137/index.html
Change-Id: I479f9e0b7ca828d048ef88b23b4948e3c1472b3c
(cherry picked from commit e3bd8dd81e51b4d02484e7eec0d725ba9c254c68)
diff --git a/media/libstagefright/httplive/M3UParser.cpp b/media/libstagefright/httplive/M3UParser.cpp
index c04549a..78a2dd0 100644
--- a/media/libstagefright/httplive/M3UParser.cpp
+++ b/media/libstagefright/httplive/M3UParser.cpp
@@ -897,6 +897,9 @@
         }
     }
 
+    if (meta->get() == NULL) {
+        return ERROR_MALFORMED;
+    }
     return OK;
 }