Bandaid for #1996 - Add null check for urlutils.

app/src/main/java/org/mozilla/focus/utils/UrlUtils.java

@@ -123,7 +123,16 @@ public static boolean isInternalErrorURL(final String url) {
         return "data:text/html;charset=utf-8;base64,".equals(url);
     }
 
-    public static boolean urlsMatchExceptForTrailingSlash(final @NonNull String url1, final @NonNull String url2) {
+    /**
+     * Checks that urls are non-null and are the same aside from a trailing slash.
+     *
+     * @return true if urls are the same except for trailing slash, or if either url is null.
+     */
+    public static boolean urlsMatchExceptForTrailingSlash(final String url1, final String url2) {
+        // This is a hack to catch a NPE in issue #26.
+        if (url1 == null || url2 == null) {
+            return false;
+        }
         int lengthDifference = url1.length() - url2.length();
 
         if (lengthDifference == 0) {

app/src/webview/java/org/mozilla/focus/webview/TrackingProtectionWebViewClient.java

@@ -103,9 +103,10 @@ public WebResourceResponse shouldInterceptRequest(final WebView view, final WebR
 
         // Don't block the main frame from being loaded. This also protects against cases where we
         // open a link that redirects to another app (e.g. to the play store).
-        final Uri pageUri = Uri.parse(currentPageURL);
         if ((!request.isForMainFrame()) &&
-                matcher.matches(resourceUri, pageUri)) {
+                currentPageURL != null &&
+                matcher.matches(resourceUri, Uri.parse(currentPageURL))) {
+                // Bandaid for issue #26: currentPageUrl can still be null, and needs to be investigated further.
             if (callback != null) {
                 callback.countBlockedTracker();
             }