Core/Updater: Fix detection of the mysql binary when a directory is given as path

This ensures that we never pass a directory path StartProcess which results in a crash.

Closes #25216

(cherry picked from commit 98b1b20d6beea5e2fdea7e404e8d880953d4b2fb)

src/server/database/Updater/DBUpdater.cpp

@@ -40,10 +40,10 @@ std::string DBUpdaterUtil::GetCorrectedMySQLExecutable()
 bool DBUpdaterUtil::CheckExecutable()
 {
     boost::filesystem::path exe(GetCorrectedMySQLExecutable());
-    if (!exists(exe))
+    if (!is_regular_file(exe))
     {
         exe = Trinity::SearchExecutableInPath("mysql");
-        if (!exe.empty() && exists(exe))
+        if (!exe.empty() && is_regular_file(exe))
         {
             // Correct the path to the cli
             corrected_path() = absolute(exe).generic_string();