diff --git a/src/blua/lvm.c b/src/blua/lvm.c
index a921d443..b654613f 100644
--- a/src/blua/lvm.c
+++ b/src/blua/lvm.c
@@ -732,7 +732,8 @@ void luaV_execute (lua_State *L, int nexeccalls) {
           luaG_runerror(L, LUA_QL("for") " limit must be a number");
         else if (!tonumber(pstep, ra+2))
           luaG_runerror(L, LUA_QL("for") " step must be a number");
-        setnvalue(ra, luai_numsub(nvalue(ra), nvalue(pstep)));
+        if (ra && pstep)
+          setnvalue(ra, luai_numsub(nvalue(ra), nvalue(pstep)));
         dojump(L, pc, GETARG_sBx(i));
         continue;
       }
diff --git a/src/command.c b/src/command.c
index 84d777ac..a15471c8 100644
--- a/src/command.c
+++ b/src/command.c
@@ -966,9 +966,11 @@ void CV_RegisterVar(consvar_t *variable)
 	// check net variables
 	if (variable->flags & CV_NETVAR)
 	{
+		const consvar_t *netvar;
 		variable->netid = CV_ComputeNetid(variable->name);
-		if (CV_FindNetVar(variable->netid))
-			I_Error("Variables %s and %s have same netid\n", variable->name, CV_FindNetVar(variable->netid)->name);
+		netvar = CV_FindNetVar(variable->netid);
+		if (netvar)
+			I_Error("Variables %s and %s have same netid\n", variable->name, netvar->name);
 	}
 
 	// link the variable in
diff --git a/src/hardware/hw_main.c b/src/hardware/hw_main.c
index 35a01ffd..ca4e000b 100644
--- a/src/hardware/hw_main.c
+++ b/src/hardware/hw_main.c
@@ -4529,7 +4529,8 @@ static void HWR_SortVisSprites(void)
 	// Fix first and last. ds still points to the last one after the loop
 	dsfirst->prev = &unsorted;
 	unsorted.next = dsfirst;
-	ds->next = &unsorted;
+	if (ds)
+		ds->next = &unsorted;
 	unsorted.prev = ds;
 
 	// pull the vissprites out by scale
@@ -4552,10 +4553,13 @@ static void HWR_SortVisSprites(void)
 				best = ds;
 			}
 		}
-		best->next->prev = best->prev;
-		best->prev->next = best->next;
-		best->next = &gr_vsprsortedhead;
-		best->prev = gr_vsprsortedhead.prev;
+		if (best)
+		{
+			best->next->prev = best->prev;
+			best->prev->next = best->next;
+			best->next = &gr_vsprsortedhead;
+			best->prev = gr_vsprsortedhead.prev;
+		}
 		gr_vsprsortedhead.prev->next = best;
 		gr_vsprsortedhead.prev = best;
 	}
diff --git a/src/hardware/r_opengl/r_opengl.c b/src/hardware/r_opengl/r_opengl.c
index 1085a712..54dd9485 100644
--- a/src/hardware/r_opengl/r_opengl.c
+++ b/src/hardware/r_opengl/r_opengl.c
@@ -1928,7 +1928,7 @@ static inline void DrawMD2Ex(INT32 *gl_cmd_buffer, md2_frame_t *frame, UINT32 du
 	//pglBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); // alpha = level of transparency
 
 	// Remove depth mask when the model is transparent so it doesn't cut thorugh sprites // SRB2CBTODO: For all stuff too?!
-	if (color[3] < 255)
+	if (color && color[3] < 255)
 	{
 		pglBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); // alpha = level of transparency
 		pglDepthMask(GL_FALSE);
diff --git a/src/r_things.c b/src/r_things.c
index eaab5361..76251d88 100644
--- a/src/r_things.c
+++ b/src/r_things.c
@@ -1634,7 +1634,8 @@ void R_SortVisSprites(void)
 	// Fix first and last. ds still points to the last one after the loop
 	dsfirst->prev = &unsorted;
 	unsorted.next = dsfirst;
-	ds->next = &unsorted;
+	if (ds)
+		ds->next = &unsorted;
 	unsorted.prev = ds;
 
 	// pull the vissprites out by scale