Hex editor memview: prevent middle mouse button from attempting to "FreezeRam" when not in RAM mode.

trunk/src/drivers/win/memview.cpp

@@ -1770,6 +1770,7 @@ LRESULT CALLBACK MemViewCallB(HWND hwnd, UINT message, WPARAM wParam, LPARAM lPa
 	}
 	case WM_MBUTTONDOWN:
 	{
+		if (EditingMode != MODE_NES_MEMORY) return 0;
 		x = GET_X_LPARAM(lParam);
 		y = GET_Y_LPARAM(lParam);
 		i = GetAddyFromCoord(x,y);