fix(exceptions): avoid trying to load when not given a source

Author: Merott

src/plugin.android.ts

@@ -18,6 +18,10 @@ export class PDFView extends common.PDFView {
   }
 
   public load(src: string) {
+    if (!src || !this.android) {
+      return;
+    }
+
     // reset any previous promise since we've called load again
     this.promise = void 0;
 

src/plugin.ios.ts

@@ -20,6 +20,10 @@ export class PDFView extends common.PDFView {
   }
 
   public load(src: string) {
+    if (!src) {
+      return;
+    }
+
     let url: NSURL;
 
     if (src.indexOf('://') === -1) {