C#: Fix crash when errors occur before language initialization.

modules/mono/csharp_script.cpp

@@ -589,7 +589,7 @@ Vector<ScriptLanguage::StackInfo> CSharpLanguage::debug_get_current_stack_info()
 		_recursion_flag_ = false;
 	};
 
-	if (!gdmono->is_runtime_initialized()) {
+	if (!gdmono || !gdmono->is_runtime_initialized()) {
 		return Vector<StackInfo>();
 	}
 
@@ -679,6 +679,7 @@ void CSharpLanguage::reload_tool_script(const Ref<Script> &p_script, bool p_soft
 
 #ifdef GD_MONO_HOT_RELOAD
 bool CSharpLanguage::is_assembly_reloading_needed() {
+	ERR_FAIL_NULL_V(gdmono, false);
 	if (!gdmono->is_runtime_initialized()) {
 		return false;
 	}
@@ -713,6 +714,7 @@ bool CSharpLanguage::is_assembly_reloading_needed() {
 }
 
 void CSharpLanguage::reload_assemblies(bool p_soft_reload) {
+	ERR_FAIL_NULL(gdmono);
 	if (!gdmono->is_runtime_initialized()) {
 		return;
 	}