Added a CodeQL workflow to check for bugs through code analysis. Fixed numerous bugs and implemented safeguards as already reported.

.github/workflows/codeql.yml

@@ -0,0 +1,32 @@
+name: "CodeQL"
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    # The branches below must be a subset of the branches above
+    branches: [ master ]
+  schedule:
+    - cron: '22 17 * * 5'
+
+jobs:
+  analyze:
+    name: Analyze
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        language: [ 'javascript' ]
+
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v2
+
+    - name: Initialize CodeQL
+      uses: github/codeql-action/init@v1
+      with:
+        languages: ${{ matrix.language }}
+
+    - name: Perform CodeQL Analysis
+      uses: github/codeql-action/analyze@v1