Fix an uninitialized value read in sqlite3async.c.

FossilOrigin-Name: 1cf2136c39239a6fea6ac2a555f55865dd517d93
diff --git a/ext/async/sqlite3async.c b/ext/async/sqlite3async.c
index 0cfc7f6..127942b 100644
--- a/ext/async/sqlite3async.c
+++ b/ext/async/sqlite3async.c
@@ -1231,8 +1231,8 @@
   */
   if( rc==SQLITE_OK ){
     int i, j;
-    int n = nPathOut;
     char *z = zPathOut;
+    int n = strlen(z);
     while( n>1 && z[n-1]=='/' ){ n--; }
     for(i=j=0; i<n; i++){
       if( z[i]=='/' ){