fixed vita startup crash by guarding commerce calls (#21)

Commerce calls are now guarded with `#elif defined(__PSVITA__) && !defined(DISABLE_PSN)`

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Co-authored-by: 552eden <552eden@gmail.com>
Reviewed-on: pieeebot/cafeberry#21
Co-authored-by: ubergamer-pie <16+ubergamer-pie@noreply.localhost>

Minecraft.Client/PSVita/PSVita_Minecraft.cpp

@@ -665,7 +665,9 @@ int main()
 	app.CommerceInit(); //  MGH - moved this here so GetCommerce isn't NULL
 
 	// 4J-PB - Kick of the check for trial or full version - requires ui to be initialised
+#ifndef DISABLE_PSN
 	app.GetCommerce()->CheckForTrialUpgradeKey();
+#endif