Fix inexplicable monkey NPE

  Bug: 8049510

Change-Id: Idbd624a309bc026a1805030982cb0cb7ace698ee
diff --git a/src/com/android/camera/FocusOverlayManager.java b/src/com/android/camera/FocusOverlayManager.java
index 2bec187..9acf85d 100644
--- a/src/com/android/camera/FocusOverlayManager.java
+++ b/src/com/android/camera/FocusOverlayManager.java
@@ -430,6 +430,7 @@
 
     public String getFocusMode() {
         if (mOverrideFocusMode != null) return mOverrideFocusMode;
+        if (mParameters == null) return Parameters.FOCUS_MODE_AUTO;
         List<String> supportedFocusModes = mParameters.getSupportedFocusModes();
 
         if (mFocusAreaSupported && mFocusArea != null) {