- treat PSP layer ID 0 as invalid

No PSprites with this ID may ever be created, as there is no means to find them again.

src/playsim/p_pspr.cpp

@@ -316,7 +316,7 @@ DPSprite *player_t::GetPSprite(PSPLayers layer)
 		newcaller = ReadyWeapon;
 	}
 
-	if (newcaller == nullptr) return nullptr; // Error case was not handled properly. This function cannot give a guarantee to always succeed!
+	if (newcaller == nullptr || layer == PSP_CALLERID) return nullptr; // Error case was not handled properly. This function cannot give a guarantee to always succeed!
 	
 	DPSprite *pspr = FindPSprite(layer);
 	if (pspr == nullptr)

src/playsim/p_pspr.h

@@ -51,6 +51,7 @@ class player_t;
 enum PSPLayers
 {
 	PSP_STRIFEHANDS = -1,
+	PSP_CALLERID = 0,
 	PSP_WEAPON = 1,
 	PSP_FLASH = 1000,
 	PSP_TARGETCENTER = INT_MAX - 2,