Don't crash if one tries to debug a qml project

Quick fix. Actually there should be IMO no way to start the debugger
for a qmlproject in the frist place.

src/plugins/debugger/debuggerrunner.cpp

@@ -131,8 +131,9 @@ DebuggerRunControl::DebuggerRunControl(DebuggerManager *manager,
         break;
     }
     if (const ProjectExplorer::Project *project = runConfiguration->project()) {
-        m_startParameters->buildDir =
-            project->activeBuildConfiguration()->buildDirectory();
+        if (project->activeBuildConfiguration())
+            m_startParameters->buildDir =
+                project->activeBuildConfiguration()->buildDirectory();
     }
     m_startParameters->useTerminal =
         runConfiguration->runMode() == LocalApplicationRunConfiguration::Console;