Fix of

Opening saved project removes Print Host settings #3655
Octoprint Settings when Opening a .3MF file #3244

When loading a configuration file (from AMF, 3MF, .ini or .gcode),
and if the host settings ("print_host", "printhost_apikey", "printhost_cafile")
in the configuration file is empty, then the config is considered to be anonymized,
and these anonymized keys are loaded from the referenced "derived from" profile,
if it exists in user's PrusaSlicer configuration directory.

We are aware that this is a patch work and a better long term solution
is to separate physical printer settings from logical printer settings,
but this is a good enough solution for PrusaSlicer 2.2.0 release.

src/libslic3r/Config.hpp

@@ -686,6 +686,7 @@ public:
     ConfigOption*           clone() const override { return new ConfigOptionString(*this); }
     ConfigOptionString&     operator=(const ConfigOption *opt) { this->set(opt); return *this; }
     bool                    operator==(const ConfigOptionString &rhs) const { return this->value == rhs.value; }
+    bool 					empty() const { return this->value.empty(); }
 
     std::string serialize() const override
     {