Fix crash when selected file has not ext

Author: bwrsandman

FileBrowser/ImGuiFileBrowser.cpp

@@ -10,9 +10,9 @@
 #include <cmath>
 
 #if defined (WIN32) || defined (_WIN32) || defined (__WIN32)
-#define OSWIN
-#ifndef NOMINMAX
-    #define NOMINMAX
+#define OSWIN
+#ifndef NOMINMAX
+    #define NOMINMAX
 #endif
 #include "Dirent/dirent.h"
 #include <windows.h>
@@ -653,9 +653,9 @@ namespace imgui_addons
 
     bool ImGuiFileBrowser::validateFile()
     {
-        int idx = selected_fn.find_last_of(".");
-        std::string ext = selected_fn.substr(idx, selected_fn.length() - idx);
-        return (std::find(valid_exts.begin(), valid_exts.end(), ext) != valid_exts.end());
+        int idx = selected_fn.find_last_of('.');
+        std::string file_ext = idx == std::string::npos ? "" : selected_fn.substr(idx, selected_fn.length() - idx);
+        return (std::find(valid_exts.begin(), valid_exts.end(), file_ext) != valid_exts.end());
     }
 
     void ImGuiFileBrowser::parsePathTabs(std::string path)