Fix crash in Pattern Language syntax highlighting for self-inheriting structs

``` rust
struct Rec : Rec {
};
```

Prevent infinite recursion in appendInheritances by erasing processed
inheritance entries during traversal, and safely iterate over
m_inheritances in appendInheritances to avoid
modification-during-iteration issues.

Author: AkiSakurai

plugins/builtin/source/content/text_highlighting/pattern_language.cpp

@@ -1603,8 +1603,10 @@ namespace hex::plugin::builtin {
     }
 
     void TextHighlighter::recurseInheritances(std::string name) {
-        if (m_inheritances.contains(name)) {
-            for (auto inheritance: m_inheritances[name]) {
+        if (auto iterator = m_inheritances.find(name); iterator != m_inheritances.end()) {
+            auto inheritances = std::move(iterator->second);
+            m_inheritances.erase(iterator);
+            for (auto inheritance: inheritances) {
                 recurseInheritances(inheritance);
                 auto definitions = m_UDTVariables[inheritance];
                 if (definitions.empty())
@@ -1628,8 +1630,8 @@ namespace hex::plugin::builtin {
     }
 
     void TextHighlighter::appendInheritances() {
-        for (auto [name, inheritances]: m_inheritances)
-            recurseInheritances(name);
+        for (auto iterator = m_inheritances.begin(); iterator != m_inheritances.end(); iterator = m_inheritances.begin())
+            recurseInheritances(iterator->first);
     }
 
 // Get the string of the argument type. This works on function arguments and non-type template arguments.