Change: mark copy-assignment as deleted for classes with a copy-constructor that is not trivial

This to prevent the default copy-assignment getting used when during the assignment also some other memory needs to be allocated as that would otherwise be freed.

src/error.h

@@ -44,6 +44,9 @@ public:
 	~ErrorMessageData();
 	ErrorMessageData(StringID summary_msg, StringID detailed_msg, uint duration = 0, int x = 0, int y = 0, const GRFFile *textref_stack_grffile = nullptr, uint textref_stack_size = 0, const uint32 *textref_stack = nullptr);
 
+	/* Remove the copy assignment, as the default implementation will not do the right thing. */
+	ErrorMessageData &operator=(ErrorMessageData &rhs) = delete;
+
 	/** Check whether error window shall display a company manager face */
 	bool HasFace() const { return face != INVALID_COMPANY; }