only initialize steam if launched from steam

docs/changelog.txt

@@ -36,6 +36,7 @@ changelog.txt uses a syntax similar to RST, with a few special sequences:
 ## New Plugins
 
 ## Fixes
+- Fix crash for some players when they launch DF outside of the Steam client
 
 ## Misc Improvements
 

library/modules/DFSteam.cpp

@@ -52,6 +52,12 @@ static void bind_all(color_ostream& out, DFLibrary* handle) {
 }
 
 bool DFSteam::init(color_ostream& out) {
+    char *steam_client_launch = getenv("SteamClientLaunch");
+    if (!steam_client_launch || strncmp(steam_client_launch, "1", 2) != 0) {
+        DEBUG(dfsteam, out).print("not launched from Steam client; not initializing steam\n");
+        return false;
+    }
+
     for (auto& lib_str : STEAM_LIBS) {
         if ((g_steam_handle = OpenPlugin(lib_str.c_str())))
             break;
@@ -168,11 +174,6 @@ void DFSteam::launchSteamDFHackIfNecessary(color_ostream& out) {
         return;
     }
 
-    if (strncmp(getenv("SteamClientLaunch"), "1", 2)) {
-        DEBUG(dfsteam, out).print("not launched from Steam client\n");
-        return;
-    }
-
     void* iSteamApps = g_SteamInternal_FindOrCreateUserInterface(g_SteamAPI_GetHSteamUser(), "STEAMAPPS_INTERFACE_VERSION008");
     if (!iSteamApps) {
         DEBUG(dfsteam, out).print("cannot obtain iSteamApps interface\n");