Added missing ramp array allocation.

src/win32_gamma.c

@@ -50,11 +50,11 @@ void _glfwPlatformGetGammaRamp(_GLFWmonitor* monitor, GLFWgammaramp* ramp)
     GetDeviceGammaRamp(dc, values);
     DeleteDC(dc);
 
+    _glfwAllocGammaRamp(ramp, 256);
+
     memcpy(ramp->red,   values +   0, 256 * sizeof(unsigned short));
     memcpy(ramp->green, values + 256, 256 * sizeof(unsigned short));
     memcpy(ramp->blue,  values + 512, 256 * sizeof(unsigned short));
-
-    ramp->size = 256;
 }
 
 void _glfwPlatformSetGammaRamp(_GLFWmonitor* monitor, const GLFWgammaramp* ramp)