- clear the Dehacked string table after passing it to GStrings.

For some reason std::move does not work here so make sure it won't stick around.

src/common/engine/stringtable.cpp

@@ -51,6 +51,7 @@ void FStringTable::LoadStrings (const char *language)
 {
 	int lastlump, lump;
 
+	allStrings.Clear();
 	lastlump = 0;
 	while ((lump = fileSystem.FindLump("LMACROS", &lastlump)) != -1)
 	{

src/common/engine/stringtable.h

@@ -87,7 +87,7 @@ public:
 	void LoadStrings(const char *language);
 	void UpdateLanguage(const char* language);
 	StringMap GetDefaultStrings() { return allStrings[default_table]; }	// Dehacked needs these for comparison
-	void SetOverrideStrings(StringMap && map)
+	void SetOverrideStrings(StringMap & map)
 	{
 		allStrings.Insert(override_table, map);
 		UpdateLanguage(nullptr);