Base: Fix memory leak in Quantity::parse

If an exception is thrown then the allocated buffer won't be cleaned up. To make this exception-safe the class
StringBufferCleaner is added using the RAII idiom

src/Base/Quantity.cpp

@@ -532,6 +532,28 @@ int QuantityLexer();
 // NOLINTNEXTLINE
 #include "QuantityLexer.c"
 #endif  // DOXYGEN_SHOULD_SKIP_THIS
+
+class StringBufferCleaner
+{
+public:
+    explicit StringBufferCleaner(YY_BUFFER_STATE buffer)
+        : my_string_buffer {buffer}
+    {}
+    ~StringBufferCleaner()
+    {
+        // free the scan buffer
+        yy_delete_buffer(my_string_buffer);
+    }
+
+    StringBufferCleaner(const StringBufferCleaner&) = delete;
+    StringBufferCleaner(StringBufferCleaner&&) = delete;
+    StringBufferCleaner& operator=(const StringBufferCleaner&) = delete;
+    StringBufferCleaner& operator=(StringBufferCleaner&&) = delete;
+
+private:
+    YY_BUFFER_STATE my_string_buffer;
+};
+
 }  // namespace QuantityParser
 
 #if defined(__clang__)
@@ -545,12 +567,11 @@ Quantity Quantity::parse(const QString& string)
     // parse from buffer
     QuantityParser::YY_BUFFER_STATE my_string_buffer =
         QuantityParser::yy_scan_string(string.toUtf8().data());
+    QuantityParser::StringBufferCleaner cleaner(my_string_buffer);
     // set the global return variables
     QuantResult = Quantity(DOUBLE_MIN);
     // run the parser
     QuantityParser::yyparse();
-    // free the scan buffer
-    QuantityParser::yy_delete_buffer(my_string_buffer);
 
     return QuantResult;
 }