Only call finishLoad() if session actually loaded.

Source/modules/encryptedmedia/MediaKeySession.cpp

Index: Source/modules/encryptedmedia/MediaKeySession.cpp
diff --git a/Source/modules/encryptedmedia/MediaKeySession.cpp b/Source/modules/encryptedmedia/MediaKeySession.cpp
index fe6455f2c34928282cec98e2953e0d8fd265ae8e..9527ce92aaf5dac968cbd542d7373219bd023382 100644
--- a/Source/modules/encryptedmedia/MediaKeySession.cpp
+++ b/Source/modules/encryptedmedia/MediaKeySession.cpp
@@ -275,6 +275,7 @@ public:
         switch (status) {
         case WebContentDecryptionModuleResult::NewSession:
             result = true;
+            m_session->finishLoad();
             break;
 
         case WebContentDecryptionModuleResult::SessionNotFound:
@@ -287,7 +288,6 @@ public:
             return;
         }
 
-        m_session->finishLoad();
         resolve(result);
     }