Added explicit test for null permissions.

This wouldn'tve actually found the problem in the previous commit,
due to the null happening before checking permissions while logging perms.
However, still seems like a nice test to have so that the method itself
handles nulls correctly.

app/src/androidTest/java/org/fdroid/fdroid/installer/ApkVerifierTest.java

@@ -99,6 +99,15 @@ public class ApkVerifierTest {
         assertTrue(extendedPermsXml.exists());
     }
 
+    @Test
+    public void testNulls() {
+        assertTrue(ApkVerifier.requestedPermissionsEqual(null, null));
+
+        String[] perms = new String[] {"Blah"};
+        assertFalse(ApkVerifier.requestedPermissionsEqual(perms, null));
+        assertFalse(ApkVerifier.requestedPermissionsEqual(null, perms));
+    }
+
     @Test
     public void testWithoutPrefix() {
         Apk apk = new Apk();