Fixes #163 - Add additional null check for breadcrumb data

Author: HazAT

android/src/main/java/io/sentry/RNSentryModule.java

@@ -166,10 +166,12 @@ public void captureBreadcrumb(ReadableMap breadcrumb) {
         if (breadcrumb.hasKey("category")) {
             breadcrumbBuilder.setCategory(breadcrumb.getString("category"));
         }
-        if (breadcrumb.hasKey("data")) {
+        if (breadcrumb.hasKey("data") && breadcrumb.getMap("data") != null) {
             Map<String, String> newData = new HashMap<>();
             for (Map.Entry<String, Object> data : breadcrumb.getMap("data").toHashMap().entrySet()) {
-                newData.put(data.getKey(), data.getValue().toString());
+                if (data.getValue() != null) {
+                    newData.put(data.getKey(), data.getValue().toString());
+                }
             }
             breadcrumbBuilder.setData(newData);
         }