Fix crash when using pnmimage.write with unsupported format, also fix a minor issue in shader.set_filename

panda/src/gobj/shader.I

@@ -56,6 +56,7 @@ get_filename(ShaderType type) const {
  */
 INLINE void Shader::
 set_filename(ShaderType type, const Filename &filename) {
+  _filename._separate = true;
   switch (type) {
   case ST_vertex:
     _filename._vertex = filename;
@@ -77,6 +78,7 @@ set_filename(ShaderType type, const Filename &filename) {
     break;
   default:
     _filename._shared = filename;
+    _filename._separate = false;
   }
 }
 

panda/src/pnmimage/pnmImageHeader.cxx

@@ -343,7 +343,7 @@ make_writer(ostream *file, bool owns_file, const Filename &filename,
     delete file;
   }
 
-  if (!writer->is_valid()) {
+  if (writer != NULL && !writer->is_valid()) {
     delete writer;
     writer = NULL;
   }