Fix wrong INTERPIC in TNT and Plutonia

See #851. Thanks @Satku0!

releasenotes.md

@@ -7,7 +7,8 @@
 * An error is no longer displayed when trying to load the *BFG Edition* of *DOOM II: Hell On Earth*.
 * Weapons that use the [*MBF21*](https://doomwiki.org/wiki/MBF21)-compatible `A_ConsumeAmmo` code pointer no longer consume ammo when fired if infinite ammo is enabled using the `infiniteammo` CCMD.
 * Animated skies defined using the [*ID24*](https://doomwiki.org/wiki/ID24)-compatible [`SKYDEFS`](https://doomwiki.org/wiki/SKYDEFS) lump are now fully supported.
-* Improvements have been made to when to clip sprites in liquid sectors when the `r_liquid_clipsprites` CVAR is `on`.
+* Improvements have been made to the clipping of sprites in liquid sectors when the `r_liquid_clipsprites` CVAR is `on`.
+* The correct `INTERPIC` lump is now always displayed when playing a PWAD for *Final DOOM: The Plutonia Experiment* or *Final DOOM: TNT - Evilution*.
 
 ![](https://github.com/bradharding/www.doomretro.com/raw/master/wiki/bigdivider.png)
 

src/wi_stuff.c

@@ -1474,9 +1474,19 @@ static void WI_LoadData(void)
     else if (gamemode == commercial)
     {
         if (gamemission == pack_plut)
-            lump = W_CacheLumpName("INTERPI2");
+        {
+            if (W_GetNumLumps("INTERPIC") > 2)
+                lump = W_CacheLumpName("INTERPIC");
+            else
+                lump = W_CacheLumpName("INTERPI2");
+        }
         else if (gamemission == pack_tnt)
-            lump = W_CacheLumpName("INTERPI3");
+        {
+            if (W_GetNumLumps("INTERPIC") > 2)
+                lump = W_CacheLumpName("INTERPIC");
+            else
+                lump = W_CacheLumpName("INTERPI3");
+        }
         else if (nerve)
             lump = W_CacheLumpNameFromResourceWAD("INTERPIC");
         else