Don't allow to open disassemble view on symbols without needed info

It's useless to offer the user the ability to open the disassembly
view on symbols without the required info - disable the actions
early to indicate that state.

Fixes: KDAB#536

src/flamegraph.cpp

@@ -904,10 +904,12 @@ bool FlameGraph::eventFilter(QObject* object, QEvent* event)
                     [this, item]() { emit jumpToCallerCallee(item->symbol()); });
             auto* openEditorAction = contextMenu.addAction(tr("Open in Editor"));
             connect(openEditorAction, &QAction::triggered, this, [this, item]() { emit openEditor(item->symbol()); });
+            openEditorAction->setEnabled(item->symbol().isValid());
             contextMenu.addSeparator();
             auto* viewDisassembly = contextMenu.addAction(tr("Disassembly"));
             connect(viewDisassembly, &QAction::triggered, this,
                     [this, item]() { emit jumpToDisassembly(item->symbol()); });
+            viewDisassembly->setEnabled(item->symbol().canDisassemble());
 
             auto* copy = contextMenu.addAction(QIcon::fromTheme(QStringLiteral("edit-copy")), tr("Copy"));
             connect(copy, &QAction::triggered, this, [item]() { qApp->clipboard()->setText(item->description()); });

src/models/data.h

@@ -64,6 +64,11 @@ struct Symbol
     {
         return !symbol.isEmpty() || !binary.isEmpty() || !path.isEmpty();
     }
+
+    bool canDisassemble() const
+    {
+        return !symbol.isEmpty() && !path.isEmpty() && relAddr > 0 && size > 0;
+    }
 };
 
 QDebug operator<<(QDebug stream, const Symbol& symbol);

src/resultsutil.cpp

@@ -113,6 +113,7 @@ void setupContextMenu(QTreeView* view, CostContextMenu* costContextMenu, int sym
                 auto* viewDisassembly = contextMenu.addAction(QCoreApplication::translate("Util", "Disassembly"));
                 QObject::connect(viewDisassembly, &QAction::triggered, &contextMenu,
                                  [symbol, callback]() { callback(CallbackAction::ViewDisassembly, symbol); });
+                viewDisassembly->setEnabled(symbol.canDisassemble());
             }
             contextMenu.addSeparator();
             costContextMenu->addToMenu(view->header(),