Core: fix minor issues:

+ fix issues found by clang's clazy tool
+ fix cppcoreguidelines-pro-type-member-init
  * Make sure that all class members are initialized in the constructor

src/Gui/DocumentRecovery.cpp

@@ -157,7 +157,7 @@ public:
         QString label;
         QString fileName;
         QString tooltip;
-        Status status;
+        Status status = Unknown;
     };
     Ui_DocumentRecovery ui;
     bool recovered;