Avoid a possible segfault crash if a nonexistant airport is specified.

diff --git a/src/Airports/runways.cxx b/src/Airports/runways.cxx
index 503f298f401b7850c00486b7a4c4fc246acd82b2..5c98af7ff46023ad8390e6524b2643a385996b28 100644 (file)
--- a/src/Airports/runways.cxx
+++ b/src/Airports/runways.cxx
@@ -149,16 +149,21 @@ bool FGRunwayList::search( const string& aptid, FGRunway* r ) {
 bool FGRunwayList::search( const string& aptid, const string& rwyno,
                            FGRunway *r )
 {
-    // standardize input number
+    string revrwyno = "";
     string runwayno = rwyno;
-    string tmp = runwayno.substr(1, 1);
-    if (( tmp == "L" || tmp == "R" || tmp == "C" ) || (runwayno.size() == 1)) {
-       tmp = runwayno;
-       runwayno = "0" + tmp;
-        SG_LOG( SG_GENERAL, SG_INFO,
-                "Standardising rwy number from " << tmp << " to " << runwayno );
+    if ( runwayno.length() ) {
+        // standardize input number
+        string tmp = runwayno.substr(1, 1);
+        if (( tmp == "L" || tmp == "R" || tmp == "C" )
+            || (runwayno.size() == 1))
+        {
+            tmp = runwayno;
+            runwayno = "0" + tmp;
+            SG_LOG( SG_GENERAL, SG_INFO, "Standardising rwy number from "
+                    << tmp << " to " << runwayno );
+        }
+        revrwyno = GetReverseRunwayNo(runwayno);
     }
-    string revrwyno = GetReverseRunwayNo(runwayno);
 
     runway_map_iterator pos;
     for ( pos = runways.lower_bound( aptid );