fix(router): avoiding throw for app stability improvements

Author: NathanWalker

Diff for: nativescript-angular/router/ns-location-strategy.ts

@@ -274,19 +274,21 @@ export class NSLocationStrategy extends LocationStrategy {
 
     // Methods for syncing with page navigation in PageRouterOutlet
     public _beginBackPageNavigation(name: string) {
-        routerLog("NSLocationStrategy.startGoBack()");
         if (this._isPageNavigationBack) {
-            throw new Error("Calling startGoBack while going back.");
+            routerLog("Warn: Attempted to call startGoBack while going back. Ignoring.");
+            return;
         }
+        routerLog("NSLocationStrategy.startGoBack()");
         this._isPageNavigationBack = true;
         this.currentOutlet = name;
     }
 
     public _finishBackPageNavigation() {
-        routerLog("NSLocationStrategy.finishBackPageNavigation()");
         if (!this._isPageNavigationBack) {
-            throw new Error("Calling endGoBack while not going back.");
+            routerLog("Warn: Attempted to call endGoBack while not going back. Ignoring.");
+            return;
         }
+        routerLog("NSLocationStrategy.finishBackPageNavigation()");
         this._isPageNavigationBack = false;
     }
 
@@ -306,18 +308,20 @@ export class NSLocationStrategy extends LocationStrategy {
     }
 
     public _beginCloseModalNavigation(): void {
-        routerLog("NSLocationStrategy.startCloseModal()");
         if (this._isModalClosing) {
-            throw new Error("Calling startCloseModal while closing modal.");
+            routerLog("Warn: Attempted to call startCloseModal while closing modal. Ignoring.");
+            return;
         }
+        routerLog("NSLocationStrategy.startCloseModal()");
         this._isModalClosing = true;
     }
 
     public _finishCloseModalNavigation() {
-        routerLog("NSLocationStrategy.finishCloseModalNavigation()");
         if (!this._isModalClosing) {
-            throw new Error("Calling startCloseModal while not closing modal.");
+            routerLog("Warn: Attempted to call startCloseModal while not closing modal. Ignoring.");
+            return;
         }
+        routerLog("NSLocationStrategy.finishCloseModalNavigation()");
         this._isModalClosing = false;
     }