Fix vector fmuladd (rust-lang#1013)

Author: wsmoses

enzyme/Enzyme/AdjointGenerator.h

@@ -4609,10 +4609,10 @@ class AdjointGenerator
         auto rule = [&](Value *dif0, Value *dif1, Value *dif2) {
           Value *dif =
               Builder2.CreateFAdd(gutils->isConstantValue(orig_ops[1])
-                                      ? Constant::getNullValue(opType1)
+                                      ? Constant::getNullValue(dif1->getType())
                                       : Builder2.CreateFMul(op0, dif1),
                                   gutils->isConstantValue(orig_ops[0])
-                                      ? Constant::getNullValue(opType2)
+                                      ? Constant::getNullValue(dif0->getType())
                                       : Builder2.CreateFMul(op1, dif0));
           return Builder2.CreateFAdd(dif, dif2);
         };