fix (Qt) issues found by clang's clazy tool:

+ -Wclazy-incorrect-emit
+ -Wclazy-strict-iterators
+ -Wclazy-overloaded-signal
+ -Wclazy-qstring-arg
+ -Wclazy-unused-non-trivial-variable
+ -Wclazy-container-anti-pattern
+ -Wclazy-range-loop-reference
+ -Wclazy-const-signal-or-slot
+ -Wclazy-detaching-temporary
+ -Wclazy-qfileinfo-exists

src/Gui/GraphvizView.cpp

@@ -87,7 +87,7 @@ public:
         // causes some problems with Qt5.
         run();
         // Can't use the finished() signal of QThread
-        emitFinished();
+        Q_EMIT emitFinished();
     }
 
     void run() {