Return driver object only when valid

Without this, a driver that failed the sanity check could be returned. This leads to attempting to use it when checking URLs, which led to avoidable failures.

Fixes urlstechie#92

urlchecker/core/urlproc.py

@@ -153,10 +153,11 @@ def get_driver(self, port: Optional[int] = None, timeout: Optional[int] = 5):
         try:
             from .webdriver import WebDriver
 
-            driver = WebDriver(port=port, timeout=timeout)
+            default_driver = WebDriver(port=port, timeout=timeout)
 
-            # Do a sanity check of the driver
-            driver.check("https://google.com")
+            # Do a sanity check of the default driver
+            default_driver.check("https://google.com")
+            driver = default_driver
         except:
             logger.warning(
                 "Issue with driver, results will be improved if you have it! Please match your version from https://googlechromelabs.github.io/chrome-for-testing"