assume beam and shockwave creation is falliable (scp-fs2open#7174)

Author: Baezon

code/ship/ship.cpp

@@ -14019,7 +14019,6 @@ void ship_process_targeting_lasers()
 
 			// hmm, why didn't it fire?
 			if(shipp->targeting_laser_objnum < 0){
-				Int3();
 				ship_stop_targeting_laser(shipp);
 			}
 		}

code/weapon/beam.cpp

@@ -698,7 +698,6 @@ int beam_fire_targeting(fighter_beam_fire_info *fire_info)
 	if(objnum < 0){
 		beam_delete(new_item);
 		nprintf(("General", "obj_create() failed for beam weapon! bah!\n"));
-		Int3();
 		return -1;
 	}
 	new_item->objnum = objnum;	

code/weapon/shockwave.cpp

@@ -181,7 +181,8 @@ int shockwave_create(int parent_objnum, const vec3d* pos, const shockwave_create
 	objnum = obj_create( OBJ_SHOCKWAVE, real_parent, i, &orient, &sw->pos, sw->outer_radius, tmp_flags + Object::Object_Flags::Renders, false );
 
 	if ( objnum == -1 ){
-		Int3();
+		mprintf(("Couldn't create shockwave object -- out of object slots\n"));
+		return -1;
 	}
 
 	sw->objnum = objnum;