Actor - use fallbacks in GetMovePathEnd()

Not doing this causes a crash when a full scene save is done and the move path happens to be empty. Happened to me multiple times over in Conquest mode (yes i know it's broken, doesn't *have* to be) when I set my brain robot on a path to dig a tunnel.

Here's a gdb backtrace of the crash:

```
[Detaching after fork from child process 73767]
/usr/include/c++/15.2.1/bits/stl_list.h:1688: std::__cxx11::list<_Tp, _Allocator>::const_reference std::__cxx11::list<_Tp, _Allocator>::back() const [with _Tp = RTE::Vector; _Alloc = std::allocator<RTE::Vector>; const_reference = const RTE::Vector&]: Assertion '!this->empty()' failed.

Thread 1 "CortexCommand" received signal SIGABRT, Aborted.
0x00007ffff6aaa0db in pthread_kill () from /usr/lib/libc.so.6
(gdb) lay src
(gdb) bt
#0  0x00007ffff6aaa0db in pthread_kill () from /usr/lib/libc.so.6
cortex-command-community#1  0x00007ffff6a447c8 in raise () from /usr/lib/libc.so.6
cortex-command-community#2  0x00007ffff6a2560d in abort () from /usr/lib/libc.so.6
cortex-command-community#3  0x00007ffff6e9870f in std::__glibcxx_assert_fail (file=<optimized out>, line=<optimized out>, function=<optimized out>, condition=<optimized out>) at /usr/src/debug/gcc/gcc/libstdc++-v3/src/c++11/assert_fail.cc:41
cortex-command-community#4  0x00005555556b7ff8 in std::__cxx11::list<RTE::Vector, std::allocator<RTE::Vector> >::back (this=0x555583892728) at /usr/include/c++/15.2.1/bits/stl_list.h:1688
cortex-command-community#5  0x0000555555890712 in RTE::Actor::GetMovePathEnd (this=0x555583891900) at ../Source/Entities/Actor.h:450
cortex-command-community#6  0x000055555588470c in RTE::Scene::SaveSceneObject (this=0x7ffe82e4bb90, writer=..., sceneObjectToSave=0x555583891900, isChildAttachable=false, saveFullData=true) at ../Source/Entities/Scene.cpp:1369
cortex-command-community#7  0x0000555555880abc in RTE::Scene::Save (this=0x7ffe82e4bb90, writer=...) at ../Source/Entities/Scene.cpp:1097
cortex-command-community#8  0x0000555555d9afca in RTE::operator<< (writer=..., operand=0x7ffe82e4bb90) at ../Source/System/Serializable.cpp:53
cortex-command-community#9  0x0000555555ad13ab in RTE::Writer::NewPropertyWithValue<RTE::Scene const*> (this=0x7fffffffcab0, propName="AddScene", propValue=@0x7fffffffc810: 0x7ffe82e4bb90) at ../Source/System/Writer.h:103
cortex-command-community#10 0x0000555555acc865 in RTE::MetaMan::Save (this=0x555557448710, writer=...) at ../Source/Managers/MetaMan.cpp:287
cortex-command-community#11 0x0000555555beb237 in RTE::MetagameGUI::SaveGame (this=0x55555ba82b20, saveName="AutoSave", savePath="Userdata/UserSavesConquest.rte/AutoSave.ini", resaveSceneData=false) at ../Source/Menus/MetagameGUI.cpp:1109
cortex-command-community#12 0x0000555555c02cbb in RTE::MetagameGUI::FinalizeOffensive (this=0x55555ba82b20) at ../Source/Menus/MetagameGUI.cpp:4458
cortex-command-community#13 0x0000555555c018d5 in RTE::MetagameGUI::UpdateOffensives (this=0x55555ba82b20) at ../Source/Menus/MetagameGUI.cpp:4321
cortex-command-community#14 0x0000555555bee37e in RTE::MetagameGUI::Update (this=0x55555ba82b20) at ../Source/Menus/MetagameGUI.cpp:1492
cortex-command-community#15 0x0000555555acf7a0 in RTE::MetaMan::Update (this=0x555557448710) at ../Source/Managers/MetaMan.cpp:892
cortex-command-community#16 0x0000555555ac2e84 in RTE::MenuMan::UpdateMetaGameMenu (this=0x55555740f4e0) at ../Source/Managers/MenuMan.cpp:221
cortex-command-community#17 0x0000555555ac2ab8 in RTE::MenuMan::Update (this=0x55555740f4e0) at ../Source/Managers/MenuMan.cpp:146
cortex-command-community#18 0x0000555555674e81 in RunMenuLoop () at ../Source/Main.cpp:272
cortex-command-community#19 0x0000555555675a55 in RunGameLoop () at ../Source/Main.cpp:374
cortex-command-community#20 0x000055555567658a in main (argc=1, argv=0x7fffffffdc88) at ../Source/Main.cpp:468
```

Doesn't crash with this applied.

Author: Architector4

Source/Entities/Actor.h

@@ -445,9 +445,19 @@ namespace RTE {
 		/// @param m_MovePath.push_back(newCoordinate The new coordinate to add to the end of the MovePath.
 		void AddToMovePathEnd(Vector newCoordinate) { m_MovePath.push_back(newCoordinate); }
 
-		/// Gets the last position in this Actor's move path.
-		/// @return The last position in this Actor's move path.
-		Vector GetMovePathEnd() const { return m_MovePath.back(); }
+		/// Gets the last position in this Actor's move path, or otherwise the current move target.
+		/// @return The last position in this Actor's move path, or otherwise the current move target.
+		Vector GetMovePathEnd() const {
+			if (!m_MovePath.empty()) {
+				return m_MovePath.back();
+			}
+			// In case move path is empty, check our own path request.
+			if (m_PathRequest) {
+				return const_cast<Vector&>(m_PathRequest->targetPos);
+			}
+			// In case *that* is empty, just return the move target.
+			return m_MoveTarget;
+		}
 
 		/// Removes a coordinate from the beginning of the MovePath, meaning the
 		/// one closest to this Actor.