Catch rendering error (FranckFreiburger#307)

* catch rendering error

* emit error event when failed cancel

* Update pdfjsWrapper.js

Co-authored-by: Bastien NOEL <[email protected]>

Author: bastiennoel93

src/pdfjsWrapper.js

@@ -193,7 +193,9 @@ export default function(PDFJS) {
 				if ( canceling )
 					return;
 				canceling = true;
-				pdfRender.cancel();
+				pdfRender.cancel().catch(function(err) {
+					emitEvent('error', err);
+				});
 				return;
 			}