Fall back on DSA-only installation checks for .pkg installations

SUBasicUpdateDriver.m

@@ -204,19 +204,20 @@ - (void)download:(NSURLDownload *)d decideDestinationWithSuggestedFilename:(NSSt
 	[download setDestination:downloadPath allowOverwrite:YES];
 }
 
-- (BOOL)validateUpdateDownloadedToPath:(NSString *)destinationPath extractedToPath:(NSString *)extractedPath DSASignature:(NSString *)DSASignature publicDSAKey:(NSString *)publicDSAKey
+- (BOOL)validateUpdateDownloadedToPath:(NSString *)downloadedPath extractedToPath:(NSString *)extractedPath DSASignature:(NSString *)DSASignature publicDSAKey:(NSString *)publicDSAKey
 {
     NSString *newBundlePath = [SUInstaller appPathInUpdateFolder:extractedPath forHost:host];
-    if (!newBundlePath) return NO;
-
-    NSError *error = nil;
-    if ([SUCodeSigningVerifier codeSignatureIsValidAtPath:newBundlePath error:&error]) {
-        return YES;
-    } else {
-        SULog(@"Code signature check on update failed: %@", error);
+    if (newBundlePath)
+    {
+        NSError *error = nil;
+        if ([SUCodeSigningVerifier codeSignatureIsValidAtPath:newBundlePath error:&error]) {
+            return YES;
+        } else {
+            SULog(@"Code signature check on update failed: %@", error);
+        }
     }
 
-    return [SUDSAVerifier validatePath:destinationPath withEncodedDSASignature:DSASignature withPublicDSAKey:publicDSAKey];
+    return [SUDSAVerifier validatePath:downloadedPath withEncodedDSASignature:DSASignature withPublicDSAKey:publicDSAKey];
 }
 
 - (void)downloadDidFinish:(NSURLDownload *)d