QGCPalette: Add missing const in SETNAME function

Signed-off-by: Patrick José Pereira <patrickelectric@gmail.com>

src/QGCPalette.h

@@ -40,7 +40,7 @@
         c << _colorInfoMap[Dark][ColorGroupDisabled][QStringLiteral(#NAME)].name(QColor::HexRgb); \
         return c; \
     } \
-    void SETNAME(QColor& color) { _colorInfoMap[_theme][_colorGroupEnabled  ? ColorGroupEnabled : ColorGroupDisabled][QStringLiteral(#NAME)] = color; _signalPaletteChangeToAll(); }
+    void SETNAME(const QColor& color) { _colorInfoMap[_theme][_colorGroupEnabled  ? ColorGroupEnabled : ColorGroupDisabled][QStringLiteral(#NAME)] = color; _signalPaletteChangeToAll(); }
 
 /*!
  QGCPalette is used in QML ui to expose color properties for the QGC palette. There are two