Check current tab before making active

      Bug: 5202966

Change-Id: I62fc806176d178193c4a9f0b658efa45b4d96584
diff --git a/src/com/android/browser/BaseUi.java b/src/com/android/browser/BaseUi.java
index 3b8ecc6..7d7fda1 100644
--- a/src/com/android/browser/BaseUi.java
+++ b/src/com/android/browser/BaseUi.java
@@ -159,7 +159,10 @@
         mActivityPaused = false;
         // check if we exited without setting active tab
         // b: 5188145
-        setActiveTab(mTabControl.getCurrentTab());
+        final Tab ct = mTabControl.getCurrentTab();
+        if (ct != null) {
+            setActiveTab(ct);
+        }
     }
 
     protected boolean isActivityPaused() {