Attempt loading of an MD2 only once; if we failed then don't bother again

This keeps my new error messages from flooding the console and log.txt

src/hardware/hw_md2.c

@@ -782,6 +782,7 @@ void HWR_InitMD2(void)
 		md2_playermodels[s].grpatch = NULL;
 		md2_playermodels[s].skin = -1;
 		md2_playermodels[s].notfound = true;
+		md2_playermodels[s].error = false;
 	}
 	for (i = 0; i < NUMSPRITES; i++)
 	{
@@ -790,6 +791,7 @@ void HWR_InitMD2(void)
 		md2_models[i].grpatch = NULL;
 		md2_models[i].skin = -1;
 		md2_models[i].notfound = true;
+		md2_models[s].error = false;
 	}
 
 	// read the md2.dat file
@@ -1282,6 +1284,8 @@ void HWR_DrawMD2(gr_vissprite_t *spr)
 		else
 			md2 = &md2_models[spr->mobj->sprite];
 
+		if (md2->error)
+			return; // we already failed loading this before :(
 		if (!md2->model)
 		{
 			//CONS_Debug(DBG_RENDER, "Loading MD2... (%s)", sprnames[spr->mobj->sprite]);
@@ -1295,6 +1299,7 @@ void HWR_DrawMD2(gr_vissprite_t *spr)
 			else
 			{
 				//CONS_Debug(DBG_RENDER, " FAILED\n");
+				md2->error = true; // prevent endless fail
 				return;
 			}
 		}

src/hardware/hw_md2.h

@@ -123,6 +123,7 @@ typedef struct
 	void        *blendgrpatch;
 	boolean     notfound;
 	INT32       skin;
+	boolean     error;
 } md2_t;
 
 extern md2_t md2_models[NUMSPRITES];