stagefright: add null guard for CameraSource::stopCameraRecording

Bug: 27120259
Change-Id: I2e081404fa4a74b286918374e7da8361c0f59d22
diff --git a/media/libstagefright/CameraSource.cpp b/media/libstagefright/CameraSource.cpp
index d302f82..64d4302 100644
--- a/media/libstagefright/CameraSource.cpp
+++ b/media/libstagefright/CameraSource.cpp
@@ -792,10 +792,14 @@
 void CameraSource::stopCameraRecording() {
     ALOGV("stopCameraRecording");
     if (mCameraFlags & FLAGS_HOT_CAMERA) {
-        mCameraRecordingProxy->stopRecording();
+        if (mCameraRecordingProxy != 0) {
+            mCameraRecordingProxy->stopRecording();
+        }
     } else {
-        mCamera->setListener(NULL);
-        mCamera->stopRecording();
+        if (mCamera != 0) {
+            mCamera->setListener(NULL);
+            mCamera->stopRecording();
+        }
     }
 }