Initialize mFp file pointer to null

Bug: 288170590
Test: atest VtsHalTvTunerTargetTest
Change-Id: Ia1d78e42094073c6cfc7e4e00d65a540d148f02e
diff --git a/tv/tuner/aidl/vts/functional/utils/IpStreamer.h b/tv/tuner/aidl/vts/functional/utils/IpStreamer.h
index d073003..8ac2ddb 100644
--- a/tv/tuner/aidl/vts/functional/utils/IpStreamer.h
+++ b/tv/tuner/aidl/vts/functional/utils/IpStreamer.h
@@ -37,7 +37,7 @@
 
   private:
     int mSockfd = -1;
-    FILE* mFp;
+    FILE* mFp = nullptr;
     bool mIsIpV4 = true;                                         // By default, set to IPV4
     int mPort = 12345;                                           // default port
     int mBufferSize = 188;                                       // bytes