Tweaks to avoid a crash when asking for FGData path

exit(-1) early in startup seems to cause QApplication to be cleaned
up in a weird way

src/GUI/SetupRootDialog.cxx

@@ -90,7 +90,7 @@ bool SetupRootDialog::runDialog(PromptState prompt)
     SetupRootDialog dlg(prompt);
     dlg.exec();
     if (dlg.result() != QDialog::Accepted) {
-        exit(-1);
+        return false;
     }
 
     return true;
@@ -104,7 +104,10 @@ SGPath SetupRootDialog::restoreUserSelectedRoot()
 	bool ask = flightgear::checkKeyboardModifiersForSettingFGRoot();
     if (ask || (path == QStringLiteral("!ask"))) {
         bool ok = runDialog(ManualChoiceRequested);
-        Q_ASSERT(ok);
+        if (!ok) {
+            exit(-1);
+        }
+
         // run dialog either exit()s or sets fg_root, so this
         // behaviour is safe and correct.
         return globals->get_fg_root();
@@ -127,7 +130,10 @@ SGPath SetupRootDialog::restoreUserSelectedRoot()
         // okay, we don't have an acceptable FG_DATA anywhere we can find, we
         // have to ask the user what they want to do.
         bool ok = runDialog(VersionCheckFailed);
-        Q_ASSERT(ok);
+        if (!ok) {
+            exit(-1);
+        }
+
         // run dialog either exit()s or sets fg_root, so this
         // behaviour is safe and correct.
         return globals->get_fg_root();

src/Main/fg_init.cxx

@@ -640,7 +640,10 @@ int fgInitConfig ( int argc, char **argv, bool reinit )
     fgSetDefaults();
     flightgear::Options* options = flightgear::Options::sharedInstance();
     if (!reinit) {
-        options->init(argc, argv, dataPath);
+        auto result = options->init(argc, argv, dataPath);
+        if (result != flightgear::FG_OPTIONS_OK) {
+            return result;
+        }
     }
 
     // establish default for developer-mode based upon compiled build types

src/Main/options.cxx

@@ -2098,7 +2098,7 @@ Options::~Options()
 {
 }
 
-void Options::init(int argc, char **argv, const SGPath& appDataPath)
+OptionResult Options::init(int argc, char** argv, const SGPath& appDataPath)
 {
 // first, process the command line
   bool inOptions = true;
@@ -2143,8 +2143,7 @@ void Options::init(int argc, char **argv, const SGPath& appDataPath)
   }
 
   if (!p->shouldLoadDefaultConfig) {
-    setupRoot(argc, argv);
-    return;
+      return setupRoot(argc, argv);
   }
 
 // then config files
@@ -2172,7 +2171,10 @@ void Options::init(int argc, char **argv, const SGPath& appDataPath)
   }
 
 // setup FG_ROOT
-  setupRoot(argc, argv);
+  auto res = setupRoot(argc, argv);
+  if (res != FG_OPTIONS_OK) {
+      return res;
+  }
 
 // system.fgfsrc is disabled, as we no longer allow anything in fgdata to set
 // fg-root/fg-home/fg-aircraft and hence control what files Nasal can access
@@ -2202,6 +2204,8 @@ void Options::init(int argc, char **argv, const SGPath& appDataPath)
       "If you created this file intentionally, please move it to '" +
       nameForError + "'.");
   }
+
+  return FG_OPTIONS_OK;
 }
 
 void Options::initPaths()
@@ -2952,14 +2956,14 @@ string_list Options::extractOptions() const
     return result;
 }
 
-void Options::setupRoot(int argc, char **argv)
+OptionResult Options::setupRoot(int argc, char** argv)
 {
     SGPath root(globals->get_fg_root());
     bool usingDefaultRoot = false;
 
     // root has already been set, so skip the fg_root setting and validation.
     if (!root.isNull()) {
-        return;
+        return FG_OPTIONS_OK;
     }
 
   if (isOptionSet("fg-root")) {
@@ -2998,7 +3002,11 @@ void Options::setupRoot(int argc, char **argv)
     // a command-line, env-var or default root this check can fail and
     // we still want to use the GUI in that case
     if (versionComp != 0) {
-        SetupRootDialog::runDialog(usingDefaultRoot);
+        flightgear::initApp(argc, argv);
+        bool ok = SetupRootDialog::runDialog(usingDefaultRoot);
+        if (!ok) {
+            return FG_OPTIONS_EXIT;
+        }
     }
 #else
     SG_UNUSED(usingDefaultRoot);
@@ -3022,6 +3030,7 @@ void Options::setupRoot(int argc, char **argv)
         std::string(FLIGHTGEAR_VERSION) + "' is required.");
   }
 #endif
+    return FG_OPTIONS_OK;
 }
 
 bool Options::shouldLoadDefaultConfig() const

src/Main/options.hxx

@@ -79,8 +79,8 @@ public:
   /**
    * pass command line arguments, read default config files
    */
-  void init(int argc, char* argv[], const SGPath& appDataPath);
-  
+  OptionResult init(int argc, char* argv[], const SGPath& appDataPath);
+
   /**
     * parse a config file (eg, .fgfsrc) 
     */
@@ -188,15 +188,16 @@ private:
 
   void processArgResult(int result);
 
-    /**
-     * Setup the root base, and check it's valid. Bails out with exit(-1) if
-     * the root package was not found or is the incorrect version. Argv/argv
+  /**
+     * Setup the root base, and check it's valid. If
+     * the root package was not found or is the incorrect version,
+     * returns FG_OPTIONS_ERROR. Argv/argv
      * are passed since we might potentially show a GUI dialog at this point
      * to help the user our (finding a base package), and hence need to init Qt.
      */
-  void setupRoot(int argc, char **argv);
+  OptionResult setupRoot(int argc, char** argv);
+
 
-  
   class OptionsPrivate;
   std::unique_ptr<OptionsPrivate> p;
 };