fix crash if FlashModes is null

Author: Marat Talipov

visionSamples/barcode-reader/app/src/main/java/com/google/android/gms/samples/vision/barcodereader/ui/camera/CameraSource.java

@@ -785,11 +785,13 @@ private Camera createCamera() {
         mFocusMode = parameters.getFocusMode();
 
         if (mFlashMode != null) {
-            if (parameters.getSupportedFlashModes().contains(
-                    mFlashMode)) {
-                parameters.setFlashMode(mFlashMode);
-            } else {
-                Log.i(TAG, "Camera flash mode: " + mFlashMode + " is not supported on this device.");
+            if (parameters.getSupportedFlashModes() != null) {
+                if (parameters.getSupportedFlashModes().contains(
+                        mFlashMode)) {
+                    parameters.setFlashMode(mFlashMode);
+                } else {
+                    Log.i(TAG, "Camera flash mode: " + mFlashMode + " is not supported on this device.");
+                }
             }
         }