Fix loads of build warnings #development

[brmassa]

When building development, the compiler raises loads of warnings (500+). There are problems are well known sources of bugs, like not checking for null.

This issue will centralize all initiatives of fixing the warnings. Warning codes sorted by frequency.

• [ ] CS8602: 158
• [ ] CS8618: 102
• [ ] CS8604: 61
• [ ] CS8600: 59
• [x] CS8625: 16
• [ ] CS1030: 11
• [x] CS0618: 11
• [x] CS8605: 11
• [ ] CS8601: 10
• [x] CS8603: 10
• [x] CS8629: 9
• [ ] CS0169: 9
• [x] CS0219: 5
• [x] CS0162: 5
• [x] CS0108: 4
• [x] CS4014: 4
• [x] CS9191: 3
• [x] CS8619: 3
• [x] CS0649: 3
• [x] CS8765: 2
• [x] CS8767: 2
• [x] CS8620: 2
• [ ] CS0067: 2
• [x] CS0659: 1
• [x] CS0661: 1
• [x] CS8714: 1
• [x] CS8607: 1
• [ ] SYSLIB0014: 1
• [x] CS8509: 1
• [x] CS1998: 1

Also, for the sake of a better code quality, we might add more rules on .editorconfig to enforce good practices.