fix "Include binary files" and "Add to Presets" will not be enabled

`IDC_SEARCHTEXT` content change relies on `CheckRegex()` to return the
length of search text to decide whether enable them.
follow-up to 0870d53

src/SearchDlg.cpp

@@ -4187,6 +4187,7 @@ int CSearchDlg::CheckRegex()
 
     auto buf                       = GetDlgItemText(IDC_SEARCHTEXT);
     int  len                       = static_cast<int>(wcslen(buf.get()));
+    int  lenSearchText             = len;
     if (IsDlgButtonChecked(*this, IDC_REGEXRADIO) == BST_CHECKED)
     {
         // check if the regex is valid
@@ -4281,7 +4282,7 @@ int CSearchDlg::CheckRegex()
     }
     RedrawWindow(GetDlgItem(*this, IDC_PATTERN), nullptr, nullptr, RDW_FRAME | RDW_INVALIDATE);
 
-    return len;
+    return lenSearchText;
 }
 
 void CSearchDlg::AutoSizeAllColumns()