fix json importer

Author: joemeszaros

src/io/import.js

@@ -78,7 +78,7 @@ class PolygonImporter extends CaveImporter {
             U.parseMyFloat(parts[2]),
             U.parseMyFloat(parts[3]),
             U.parseMyFloat(parts[4]),
-            parts[10]
+            parts[10] === '' ? undefined : parts[10]
           )
         );
       }
@@ -320,7 +320,7 @@ class JsonImporter extends CaveImporter {
     this.attributeDefs = attributeDefs;
   }
 
-  importFile(file, name, onCaveLoad, endcoding = 'iso_8859-2') {
+  importFile(file, name, onCaveLoad, endcoding = 'utf8') {
     super.importFile(file, name, onCaveLoad, endcoding);
   }
 

src/model/survey.js

@@ -104,7 +104,9 @@ class Shot {
   toExport() {
     let newShot = {};
     this.export_fields.forEach((fName) => {
-      newShot[fName] = this[fName];
+      if (this[fName] !== undefined && this[fName] !== null) {
+        newShot[fName] = this[fName];
+      }
     });
     return newShot;
   }