Fix/handle safe low undefined (#10561)

* fix: handle safeLow undefined

fixes #10558

* fix: add tests for isCustomGasPriceSafe selector

ui/app/selectors/custom-gas.js

@@ -64,7 +64,7 @@ export function isCustomPriceSafe(state) {
     return true;
   }
 
-  if (safeLow === null) {
+  if (!safeLow) {
     return false;
   }
 

ui/app/selectors/tests/custom-gas.test.js

@@ -6,6 +6,7 @@ const {
   getCustomGasPrice,
   getRenderableBasicEstimateData,
   getRenderableEstimateDataForSmallButtonsFromGWEI,
+  isCustomPriceSafe,
 } = proxyquire('../custom-gas', {});
 
 describe('custom-gas selectors', function () {
@@ -15,6 +16,44 @@ describe('custom-gas selectors', function () {
       assert.strictEqual(getCustomGasPrice(mockState), 'mockPrice');
     });
   });
+  describe('isCustomGasPriceSafe()', function () {
+    it('should return true for gas.customData.price 0x77359400', function () {
+      const mockState = {
+        gas: {
+          customData: { price: '0x77359400' },
+          basicEstimates: { safeLow: 1 },
+        },
+      };
+      assert.strictEqual(isCustomPriceSafe(mockState), true);
+    });
+    it('should return true for gas.customData.price null', function () {
+      const mockState = {
+        gas: {
+          customData: { price: null },
+          basicEstimates: { safeLow: 1 },
+        },
+      };
+      assert.strictEqual(isCustomPriceSafe(mockState), true);
+    });
+    it('should return true gas.customData.price undefined', function () {
+      const mockState = {
+        gas: {
+          customData: { price: undefined },
+          basicEstimates: { safeLow: 1 },
+        },
+      };
+      assert.strictEqual(isCustomPriceSafe(mockState), true);
+    });
+    it('should return false gas.basicEstimates.safeLow undefined', function () {
+      const mockState = {
+        gas: {
+          customData: { price: '0x77359400' },
+          basicEstimates: { safeLow: undefined },
+        },
+      };
+      assert.strictEqual(isCustomPriceSafe(mockState), false);
+    });
+  });
 
   describe('getCustomGasLimit()', function () {
     it('should return gas.customData.limit', function () {