Fix crash when saving read-only palette file

toonz/sources/toonzlib/studiopalette.cpp

@@ -579,6 +579,13 @@ void StudioPalette::setStylesGlobalNames(TPalette *palette) {
 //-------------------------------------------------------------------
 
 void StudioPalette::save(const TFilePath &path, TPalette *palette) {
+  TFileStatus fs(path);
+  if (!fs.isWritable()) {
+    throw TSystemException(path,
+                           "The studio palette cannot be saved: it is a read "
+                           "only studio palette.");
+  }
+
   TOStream os(path);
   std::map<std::string, std::string> attr;
   attr["name"] = ::to_string(palette->getGlobalName());

toonz/sources/toonzlib/txshpalettelevel.cpp

@@ -101,6 +101,11 @@ void TXshPaletteLevel::load() {
 void TXshPaletteLevel::save() {
   TFilePath path = getScene()->decodeFilePath(m_path);
   if (TSystem::doesExistFileOrLevel(path) && m_palette) {
+    TFileStatus fs(path);
+    if (!fs.isWritable()) {
+      throw TSystemException(
+          path, "The palette cannot be saved: it is a read only palette.");
+    }
     TOStream os(path);
     os << m_palette;
   }

toonz/sources/toonzqt/paletteviewer.cpp

@@ -22,6 +22,7 @@
 
 // TnzCore includes
 #include "tconvert.h"
+#include "tsystem.h"
 
 // Qt includes
 #include <QVBoxLayout>
@@ -894,8 +895,15 @@ void PaletteViewer::saveStudioPalette() {
         int ret = DVGui::MsgBox(question, QObject::tr("Overwrite"),
                                 QObject::tr("Don't Overwrite"), 0);
         if (ret == 2 || ret == 0) return;
-        StudioPalette::instance()->save(palettePath, palette);
-        palette->setDirtyFlag(false);
+        try {
+          StudioPalette::instance()->save(palettePath, palette);
+          palette->setDirtyFlag(false);
+        } catch (TSystemException se) {
+          QApplication::restoreOverrideCursor();
+          DVGui::warning(QString::fromStdWString(se.getMessage()));
+          return;
+        } catch (...) {
+        }
       }
     }
     return;