[fbx] Fix #44371 #44376 File crash and Buffer Overflow

Fixes:
- Element collection will only contain valid elements.
- Fixes buffer overflow in the FBX document

modules/fbx/editor_scene_importer_fbx.cpp

@@ -128,7 +128,7 @@ Node *EditorSceneImporterFBX::import_scene(const String &p_path, uint32_t p_flag
 			FBXDocParser::TokenizeBinary(tokens, (const char *)data.write().ptr(), (size_t)data.size());
 		} else {
 			print_verbose("[doc] is ascii");
-			FBXDocParser::Tokenize(tokens, (const char *)data.write().ptr());
+			FBXDocParser::Tokenize(tokens, (const char *)data.write().ptr(), (size_t)data.size());
 		}
 
 		// The import process explained:

modules/fbx/fbx_parser/FBXMeshGeometry.cpp

@@ -182,7 +182,7 @@ MeshGeometry::MeshGeometry(uint64_t id, const ElementPtr element, const std::str
 
 		// This is stupid, because it means we select them ALL not just the one we want.
 		// but it's fine we can match by id.
-		GetRequiredElement(top, layer_type_name);
+
 		const ElementCollection &candidates = top->GetCollection(layer_type_name);
 
 		ElementMap::const_iterator iter;

modules/fbx/fbx_parser/FBXTokenizer.cpp

@@ -142,7 +142,7 @@ void ProcessDataToken(TokenList &output_tokens, const char *&start, const char *
 } // namespace
 
 // ------------------------------------------------------------------------------------------------
-void Tokenize(TokenList &output_tokens, const char *input) {
+void Tokenize(TokenList &output_tokens, const char *input, size_t length) {
 	// line and column numbers numbers are one-based
 	unsigned int line = 1;
 	unsigned int column = 1;
@@ -152,8 +152,13 @@ void Tokenize(TokenList &output_tokens, const char *input) {
 	bool pending_data_token = false;
 
 	const char *token_begin = nullptr, *token_end = nullptr;
-	for (const char *cur = input; *cur; column += (*cur == '\t' ? ASSIMP_FBX_TAB_WIDTH : 1), ++cur) {
-		const char c = *cur;
+
+	// input (starting string), *cur the current string, column +=
+	// modified to fix strlen() and stop buffer overflow
+	for (size_t x = 0; x < length; x++) {
+		const char c = input[x];
+		const char *cur = &input[x];
+		column += (c == '\t' ? ASSIMP_FBX_TAB_WIDTH : 1);
 
 		if (IsLineEnd(c)) {
 			comment = false;

modules/fbx/fbx_parser/FBXTokenizer.h

@@ -187,7 +187,7 @@ typedef std::vector<TokenPtr> TokenList;
  * @param output_tokens Receives a list of all tokens in the input data.
  * @param input_buffer Textual input buffer to be processed, 0-terminated.
  * @print_error if something goes wrong */
-void Tokenize(TokenList &output_tokens, const char *input);
+void Tokenize(TokenList &output_tokens, const char *input, size_t length);
 
 /** Tokenizer function for binary FBX files.
  *