fix fuzzer

turn asserts into error returns to fix fuzz

R=kjlubick@google.com
BUG=skia:6162

Change-Id: I7508eb5cb41425dcfc2718aaa9cc1ee8aa00acc9
Reviewed-on: https://skia-review.googlesource.com/9118
Reviewed-by: Kevin Lubick <kjlubick@google.com>
Commit-Queue: Cary Clark <caryclark@google.com>

src/pathops/SkIntersections.cpp

@@ -82,8 +82,12 @@ int SkIntersections::insert(double one, double two, const SkDPoint& pt) {
         fIsCoincident[1] += fIsCoincident[1] & clearMask;
     }
     fPt[index] = pt;
-    SkASSERT(one >= 0 && one <= 1);
-    SkASSERT(two >= 0 && two <= 1);
+    if (one < 0 || one > 1) {
+        return -1;
+    }
+    if (two < 0 || two > 1) {
+        return -1;
+    }
     fT[0][index] = one;
     fT[1][index] = two;
     ++fUsed;