Extensions: only perform URL check in addExtension if we already have the URL

Bug: 1093731
Change-Id: I3e948970782491ec4eb31bca603c2bd05aa1287a
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2242769
Reviewed-by: Tim van der Lippe <[email protected]>
Commit-Queue: Andrey Kosyakov <[email protected]>
diff --git a/front_end/extensions/ExtensionServer.js b/front_end/extensions/ExtensionServer.js
index 38180f5..843b38f 100644
--- a/front_end/extensions/ExtensionServer.js
+++ b/front_end/extensions/ExtensionServer.js
@@ -746,7 +746,7 @@
     const startPage = extensionInfo.startPage;
 
     const inspectedURL = SDK.SDKModel.TargetManager.instance().mainTarget().inspectedURL();
-    if (!this._canInspectURL(inspectedURL)) {
+    if (inspectedURL !== '' && !this._canInspectURL(inspectedURL)) {
       this._disableExtensions();
     }
     if (!this._extensionsEnabled) {