add null check for fingerprintmanager

app/src/main/java/com/besendorf/androidsecurityscanner/MainActivity.java

@@ -237,6 +237,9 @@ public class MainActivity extends AppCompatActivity {
         if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
             //Get an instance of FingerprintManager//
             fingerprintManager = (FingerprintManager) getSystemService(FINGERPRINT_SERVICE);
+            if (fingerprintManager == null){
+                return false;
+            }
             return fingerprintManager.isHardwareDetected();
         }
         return false;