Crashed while converting image to PDF

[ghost]

Following is crash log

Crashed: com.apple.main-thread
0 CoreFoundation 0x18574d10c CFRelease + 1128
1 libPDFRIP.A.dylib 0x185e1339c PDFImageEmitDefinition
2 CoreFoundation 0x1857502cc __CFSetApplyFunction_block_invoke + 24
3 CoreFoundation 0x1857500fc CFBasicHashApply + 128
4 CoreFoundation 0x185750028 CFSetApplyFunction + 200
5 libPDFRIP.A.dylib 0x185e13ddc PDFImageSetEmitDefinitions
6 libPDFRIP.A.dylib 0x185e0d36c emit_page_resources(PDFDocument*)
7 libPDFRIP.A.dylib 0x185e0d2f8 PDFDocumentEndPage
8 libPDFRIP.A.dylib 0x185e0bfd4 pdf_EndPage
9 iFax iOS 0x100472aa4 specialized static NSData.convertImageToPDF(image : UIImage, horizontalResolution : Double, verticalResolution : Double) -> NSData? (NSData+ImageToPDFConverter+Swift3.swift:42)
10 iFax iOS 0x1004728c8 @objc static NSData.convertImageToPDF(image : UIImage, horizontalResolution : Double, verticalResolution : Double) -> NSData? (NSData+ImageToPDFConverter+Swift3.swift)
11 iFax iOS 0x10047287c @objc static NSData.convertImageToPDF(image : UIImage, resolution : Double) -> NSData? (NSData+ImageToPDFConverter+Swift3.swift:20)
12 iFax iOS 0x100472824 @objc static NSData.convertImageToPDF(image : UIImage) -> NSData? (NSData+ImageToPDFConverter+Swift3.swift:16)
13 iFax iOS 0x10028ffa4 specialized PDFFromImage(UIImage, imageName : String, path : URL) -> URL (CommonFunctions.swift:539)
14 iFax iOS 0x1001d389c PreviewController.shareOutgoingFax() -> URL (CommonFunctions.swift)
15 iFax iOS 0x1001dfd08 specialized PreviewController.shareButtonTapped(UIBarButtonItem) -> () (PreviewController.swift:977)
16 iFax iOS 0x1001d2d0c @objc PreviewController.backButtonClicked(UIButton) -> () + 4296486156
17 UIKit 0x18adfa3c8 -[UIApplication sendAction:to:from:forEvent:] + 100
18 UIKit 0x18af793dc -[UIBarButtonItem(UIInternal) _sendAction:withEvent:] + 168
19 UIKit 0x18adfa3c8 -[UIApplication sendAction:to:from:forEvent:] + 100
20 UIKit 0x18adfa344 -[UIControl sendAction:to:forEvent:] + 80
21 UIKit 0x18ade2c6c -[UIControl _sendActionsForEvents:withEvent:] + 416
22 UIKit 0x18ade2db8 -[UIControl _sendActionsForEvents:withEvent:] + 748
23 UIKit 0x18adf9c5c -[UIControl touchesEnded:withEvent:] + 572
24 UIKit 0x18adb4bdc _UIGestureRecognizerUpdate + 9124
25 CoreFoundation 0x185823c30 CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION + 32
26 CoreFoundation 0x1858219d4 __CFRunLoopDoObservers + 372
27 CoreFoundation 0x185821e04 __CFRunLoopRun + 928
28 CoreFoundation 0x185750dc0 CFRunLoopRunSpecific + 384
29 GraphicsServices 0x1908a4088 GSEventRunModal + 180
30 UIKit 0x18ae2af44 UIApplicationMain + 204
31 iFax iOS 0x1000d43e0 main (AppDelegate.swift:106)
32 libdyld.dylib 0x19ac8e8b8 start + 4

[ghost]

can you please help to fix this crash?