initialize m_numTypes in DisassemblyModel

the value is not initialized and can cause QAbstractHeaderView to crash
this might fix #337

Author: lievenhey

src/models/disassemblymodel.h

@@ -47,5 +47,5 @@ class DisassemblyModel : public QAbstractTableModel
 private:
     DisassemblyOutput m_data;
     Data::CallerCalleeResults m_results;
-    int m_numTypes;
+    int m_numTypes = 0;
 };