handle "$(inherited)" library search paths value

fixes #15

Author: alunny

lib/pbxProject.js

@@ -456,13 +456,15 @@ pbxProject.prototype.removeFromLibrarySearchPaths = function (file) {
         if (unquote(buildSettings['PRODUCT_NAME']) != this.productName)
             continue;
 
-        if (buildSettings[SEARCH_PATHS]) {
-            var matches = buildSettings[SEARCH_PATHS].filter(function(p) {
+        searchPaths = buildSettings[SEARCH_PATHS];
+
+        if (searchPaths) {
+            var matches = searchPaths.filter(function(p) {
                 return p.indexOf(new_path) > -1;
             });
             matches.forEach(function(m) {
-                var idx = buildSettings[SEARCH_PATHS].indexOf(m);
-                buildSettings[SEARCH_PATHS].splice(idx, 1);
+                var idx = searchPaths.indexOf(m);
+                searchPaths.splice(idx, 1);
             });
         }
 
@@ -480,7 +482,8 @@ pbxProject.prototype.addToLibrarySearchPaths = function (file) {
         if (unquote(buildSettings['PRODUCT_NAME']) != this.productName)
             continue;
 
-        if (!buildSettings['LIBRARY_SEARCH_PATHS']) {
+        if (!buildSettings['LIBRARY_SEARCH_PATHS']
+                || buildSettings['LIBRARY_SEARCH_PATHS'] === INHERITED) {
             buildSettings['LIBRARY_SEARCH_PATHS'] = [INHERITED];
         }
 
@@ -610,7 +613,8 @@ function correctForResourcesPath(file, project) {
 }
 
 function searchPathForFile(file, proj) {
-    var pluginsPath = proj.pbxGroupByName('Plugins').path,
+    var plugins = proj.pbxGroupByName('Plugins')
+        pluginsPath = plugins ? plugins.path : null,
         fileDir = path.dirname(file.path);
 
     if (fileDir == '.') {