minor cleanup and remove arbitrary limit. Still limited to 500 objects.

Author: MjnMixael

code/globalincs/globals.h

@@ -34,9 +34,6 @@
 #define MAX_SHIPS					500		// max number of ship instances there can be.DTP; bumped from 200 to 400, then to 500 in 2022
 #define SHIPS_LIMIT					500		// what MAX_SHIPS will be at release time (for error checking in debug mode); dtp Bumped from 200 to 400, then to 500 in 2022
 
-// from prop.h
-#define MAX_PROPS               200 // Arbitrary guess
-
 // from missionparse.h and then redefined to the same value in sexp.h
 #define TOKEN_LENGTH	32
 

code/mission/missionparse.cpp

@@ -4997,7 +4997,6 @@ void parse_props(mission* pm)
 {
 	if (optional_string("#Props")) {
 		while (required_string_either("#Events", "$Name:")) {
-			Assert(Parse_props.size() < MAX_PROPS);
 			parse_prop(pm);
 		}
 	}

code/prop/prop.cpp

@@ -251,17 +251,6 @@ int prop_create(matrix* orient, vec3d* pos, int prop_type, const char* name)
 	prop_info* pip;
 	prop* propp;
 
-	if (Props.size() >= MAX_PROPS) {
-		if (!Fred_running) {
-			Error(LOCATION,
-				"There is a limit of %d props in the mission at once.  Please be sure that you do not have more "
-				"than %d props present in the mission at the same time.",
-				MAX_PROPS,
-				MAX_PROPS);
-		}
-		return -1;
-	}
-
 	Assertion((prop_type >= 0) && (prop_type < static_cast<int>(Prop_info.size())),
 		"Invalid prop_type %d passed to prop_create() (expected value in the range 0-%d)\n",
 		prop_type,
@@ -834,7 +823,7 @@ int prop_check_collision(object* prop_obj, object* other_obj, vec3d* hitpos, col
 				asteroid* astp = &Asteroids[instance];
 				mc.model_instance_num = astp->model_instance_num;
 				mc.model_num = Asteroid_info[astp->asteroid_type].subtypes[astp->asteroid_subtype].model_number;	
-				mc.submodel_num - 1; // Typo from asteroth?
+				mc.submodel_num = -1;
 			}
 
 			mc.orient = &heavy_obj->orient;				// The object's orient

code/prop/prop.h

@@ -47,9 +47,13 @@ typedef struct parsed_prop {
 
 extern bool Props_inited;
 
-// Global prop info array
+// Global prop info
 extern SCP_vector<prop_info> Prop_info;
 
+// Global prop objects. Vector of optionals so that we can have stable indices
+// and still be able to remove props. Deleted props are set to std::nullopt
+// so any access should check if the optional has a value first.
+// The vector is cleared at the end of each mission, never during.
 extern SCP_vector<std::optional<prop>> Props;
 
 inline int prop_info_size()